Light-emitting device and peeling method

ABSTRACT

A flexible device is provided. The hardness of a bonding layer of the flexible device is set to be higher than Shore D of 70, or preferably higher than or equal to Shore D of 80. The coefficient of expansion of a flexible substrate of the flexible device is set to be less than 58 ppm/° C., or preferably less than or equal to 30 ppm/° C.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/252,295, filed Aug. 31, 2016, now allowed, which continuation of U.S.application Ser. No. 14/621,914, filed Feb. 13, 2015, now U.S. Pat. No.9,437,832, which claims the benefit of a foreign priority applicationfiled in Japan as Serial No. 2014-029756 on Feb. 19, 2014, all of whichare incorporated by reference.

TECHNICAL FIELD

One embodiment of the present invention relates to a light-emittingdevice, a display device, an electronic device, a lighting device, or amanufacturing method thereof. In particular, one embodiment of thepresent invention relates to a light-emitting device, a display device,an electronic device, or a lighting device utilizing anelectroluminescence (hereinafter also referred to as EL) phenomenon, anda manufacturing method thereof. In particular, one embodiment of thepresent invention relates to a peeling method and a method formanufacturing a device including a peeling process.

Note that one embodiment of the present invention is not limited to theabove technical field. One embodiment of the invention disclosed in thisspecification and the like relates to an object, a method, or amanufacturing method. In addition, one embodiment of the presentinvention relates to a process, a machine, manufacture, or a compositionof matter. Specifically, examples of the technical field of oneembodiment of the present invention disclosed in this specification caninclude a semiconductor device, a display device, a light-emittingdevice, a power storage device, a storage device, a method for drivingany of them, and a method for manufacturing any of them.

BACKGROUND ART

In recent years, a flexible device in which a functional element such asa semiconductor element, a display element, or a light-emitting elementis provided over a substrate having flexibility (hereinafter alsoreferred to as a flexible substrate) has been developed. Typicalexamples of the flexible device include, as well as a lighting deviceand an image display device, a variety of semiconductor circuitsincluding a semiconductor element such as a transistor.

As a method for manufacturing a device including a flexible substrate, atechnique has been developed in which a functional element such as athin film transistor or an organic EL element is formed over a formationsubstrate (e.g., a glass substrate or a quartz substrate), and then thefunctional element is transferred to a flexible substrate. Thistechnique needs a step of peeling a layer including the functionalelement from the formation substrate (also referred to as a peelingprocess).

For example, Patent Document 1 discloses the following peeling techniqueusing laser ablation: a separation layer formed of amorphous silicon orthe like is formed over a substrate, a layer to be peeled which isformed of a thin film element is formed over the separation layer, andthe layer to be peeled is bonded to a transfer body with the use of abonding layer. The separation layer is ablated by laser lightirradiation, so that peeling is generated in the separation layer.

In addition, Patent Document 2 discloses a technique in which peeling isconducted by physical force such as human hands. In addition, PatentDocument 2 discloses the following peeling technique: a metal layer isformed between a substrate and an oxide layer and peeling is generatedat an interface between the oxide layer and the metal layer by utilizingweak bonding at the interface between the oxide layer and the metallayer, so that a layer to be peeled and the substrate are separated fromeach other.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No. H10-125931

[Patent Document 2] Japanese Published Patent Application No.2003-174153 DISCLOSURE OF INVENTION

One object of one embodiment of the present invention is to improveyield in a peeling process. Another object of one embodiment of thepresent invention is to suppress occurrence of a crack in an inorganicinsulating film or the like (breaking or cracking the film) in a peelingprocess.

Another object of one embodiment of the present invention is to improveyield in a manufacturing process of a device such as a semiconductordevice, a light-emitting device, a display device, an electronic device,or a lighting device. In particular, another object of one embodiment ofthe present invention is to improve yield in a manufacturing process ofa device such as a semiconductor device, a light-emitting device, adisplay device, an electronic device, or a lighting device which islightweight, thin, or flexible. Another object of one embodiment of thepresent invention is to suppress occurrence of a crack in an inorganicinsulating film or the like in a manufacturing process of a device.Another object of one embodiment of the present invention is to providea method for manufacturing a device with high mass productivity.

Another object of one embodiment of the present invention is to providea highly reliable device. Another object of one embodiment of thepresent invention is to provide a device with high resistance torepeated bending. Another object of one embodiment of the presentinvention is to provide a novel semiconductor device, light-emittingdevice, display device, electronic device, or lighting device.

Another object of one embodiment of the present invention is to reducethe amount of dust generated in a manufacturing process of the device.Another object of one embodiment of the present invention is to suppressentry of impurities in a manufacturing process of the device. Anotherobject of one embodiment of the present invention is to improvealignment accuracy at the time of attachment of substrates in amanufacturing process of the device. Another object of one embodiment ofthe present invention is to provide a novel peeling method or a novelmethod for manufacturing the device.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all the objects. Other objects will be apparent fromand can be derived from the description of the specification, thedrawings, the claims, and the like.

One embodiment of the present invention is a light-emitting deviceincluding a first substrate, a second substrate, an element layer, afirst bonding layer, a second bonding layer, and an insulating layer.The first substrate and the second substrate have flexibility. Theelement layer is provided between the first substrate and the secondsubstrate. The element layer includes a light-emitting element. Theinsulating layer is provided between the first substrate and the elementlayer. The first bonding layer is provided between the first substrateand the insulating layer. The second bonding layer is provided betweenthe second substrate and the element layer. The first bonding layerincludes a first portion. The second bonding layer includes a secondportion. Hardness of the first portion is higher than Shore D (alsoreferred to as shore D hardness) of 70. Hardness of the second portionis higher than shore D of 70. The first substrate includes a thirdportion. The second substrate includes a fourth portion. A coefficientof expansion of the third portion is less than 58 ppm/° C. A coefficientof expansion of the fourth portion is less than 58 ppm/° C.

In the above light-emitting device, it is preferable that the hardnessof the first portion be higher than or equal to Shore D of 80 and thatthe hardness of the second portion be higher than or equal to Shore D of80.

In the above light-emitting device, it is preferable that thecoefficient of expansion of the third portion be less than or equal to30 ppm/° C. and that the coefficient of expansion of the fourth portionbe less than or equal to 30 ppm/° C.

Another embodiment of the present invention is a peeling methodincluding a first step, a second step, a third step, a fourth step, afifth step, and a sixth step. The first step includes a step of forminga peeling layer over a first substrate. The second step includes a stepof forming a layer to be peeled over the peeling layer. The layer to bepeeled includes a first layer. The first layer includes a region incontact with the peeling layer. The third step includes a step ofdisposing a bonding layer so as to overlap with the peeling layer andthe layer to be peeled. A sheet-like adhesive is used for the bondinglayer. The fourth step includes a step of curing the bonding layer. Thefifth step includes a step of removing a first portion. The first layerincludes the first portion. The first portion includes a regionoverlapping with the peeling layer and the bonding layer. The sixth stepincludes a step of separating the peeling layer and the layer to bepeeled from each other.

In the above peeling method, in the fifth step, the first portion ispreferably removed by laser light irradiation.

In the above peeling method, in the third step, the peeling layer andthe bonding layer preferably overlap with each other so that an endportion of the bonding layer is positioned on an inner side than an endportion of the peeling layer.

In the above peeling method, the bonding layer cured in the fourth steppreferably has a portion having hardness higher than Shore D of 70. Itis particularly preferable that the bonding layer have a portion havinghardness higher than or equal to Shore D of 80.

In addition, the light-emitting device of one embodiment of the presentinvention includes a first flexible substrate; a second flexiblesubstrate; an element layer including a light-emitting element, betweenthe first flexible substrate and the second flexible substrate; aninsulating layer between the first flexible substrate and the elementlayer; a first bonding layer between the first flexible substrate andthe insulating layer; and a second bonding layer between the secondflexible substrate and the element layer. The light-emitting elementincludes a layer containing a light-emitting organic compound between apair of electrodes.

In the above light-emitting device, at least one of hardness of thefirst bonding layer and hardness of the second bonding layer ispreferably higher than Shore D of 70, or further preferably higher thanor equal to Shore D of 80.

In the above light-emitting device, at least one of the coefficient ofexpansion of the first flexible substrate and the coefficient ofexpansion of the second flexible substrate is preferably less than 58ppm/° C., or further preferably less than or equal to 30 ppm/° C.

A peeling method according to one embodiment of the present inventionincludes a first step of forming a peeling layer over a first substrate,a second step of forming a layer to be peeled including a first layer incontact with the peeling layer over the peeling layer, a third step ofcuring a bonding layer in an overlapping manner with the peeling layerand the layer to be peeled, a fourth step of removing part of the firstlayer overlapping with the peeling layer and the bonding layer to form apeeling starting point, and a fifth step of separating the peeling layerand the layer to be peeled. Note that a sheet-like adhesive is used forthe bonding layer.

In the above peeling method, the peeling starting point is preferablyformed by laser light irradiation.

In the above peeling method, the layer to be peeled preferably includesan inorganic insulating film. For example, the first layer may be aninorganic insulating film.

In the above peeling method, the peeling layer and the bonding layerpreferably overlap with each other so that an end portion of the bondinglayer is positioned on an inner side than an end portion of the peelinglayer.

In the above peeling method, the hardness of the bonding layer in acured state is preferably higher than Shore D of 70, or furtherpreferably higher than or equal to Shore D of 80.

Note that the light-emitting device in this specification includes, inits category, a display device using a light-emitting element.Furthermore, the light-emitting device may be included in a module inwhich a light-emitting element is provided with a connector such as ananisotropic conductive film or a TCP (tape carrier package); a modulehaving a TCP at the tip of which a printed wiring board is provided; anda module in which an IC (integrated circuit) is directly mounted on alight-emitting element by a COG (chip on glass) method. Moreover,lighting equipment or the like may include the light-emitting device.

According to one embodiment of the present invention, yield in a peelingprocess can be improved. According to one embodiment of the presentinvention, occurrence of a crack in an inorganic insulating film or thelike in a peeling process can be suppressed.

Moreover, according to one embodiment of the present invention, yield ina manufacturing process of a device such as a semiconductor device, alight-emitting device, a display device, an electronic device, or alighting device can be improved. In particular, yield in a manufacturingprocess of a device such as a semiconductor device, a light-emittingdevice, a display device, an electronic device, or a lighting devicewhich is lightweight, thin, or flexible can be improved. According toone embodiment of the present invention, occurrence of a crack in aninorganic insulating film or the like in a manufacturing process of thedevice can be suppressed. According to one embodiment of the presentinvention, a method for manufacturing a device with high massproductivity can be provided.

In addition, according to one embodiment of the present invention, ahighly reliable device can be provided. According to one embodiment ofthe present invention, a device with high resistance to repeated bendingcan be provided. According to one embodiment of the present invention, anovel device such as a semiconductor device, a light-emitting device, adisplay device, an electronic device, or a lighting device can beprovided.

Furthermore, according to one embodiment of the present invention, theamount of dust generated in a manufacturing process of the device can bereduced. According to one embodiment of the present invention, entry ofimpurities in a manufacturing process of the device can be suppressed.According to one embodiment of the present invention, alignment accuracyat the time of attachment of substrates in a manufacturing process ofthe device can be improved. According to one embodiment of the presentinvention, a novel peeling method or a novel method for manufacturingthe device can be provided.

Note that the description of these effects does not disturb theexistence of other effects. One embodiment of the present invention doesnot necessarily achieve all the above effects. Other effects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1F illustrate an example of a method for manufacturing alight-emitting device.

FIGS. 2A to 2E illustrate an example of a method for manufacturing alight-emitting device.

FIGS. 3A to 3D illustrate examples of a light-emitting device.

FIGS. 4A to 4E illustrate examples of a light-emitting device.

FIGS. 5A to 5E illustrate a peeling method.

FIGS. 6A to 6D illustrate a peeling method.

FIGS. 7A, 7B1, 7B2, 7B3, 7B4, 7B5, and 7C illustrate a peeling method.

FIGS. 8A to 8D illustrate a peeling method.

FIGS. 9A to 9D illustrate a peeling method.

FIGS. 10A to 10D illustrate a peeling method.

FIGS. 11A to 11C illustrate a peeling method.

FIGS. 12A to 12I illustrate planar shapes of a peeling layer.

FIGS. 13A to 13C illustrate a method for manufacturing a light-emittingdevice.

FIGS. 14A to 14C illustrate a method for manufacturing a light-emittingdevice.

FIGS. 15A to 15C illustrate a method for manufacturing a light-emittingdevice.

FIGS. 16A to 16C illustrate a method for manufacturing a light-emittingdevice.

FIGS. 17A and 17B illustrate a method for manufacturing a light-emittingdevice.

FIG. 18 is a photograph showing a light-emitting device undermanufacture.

FIGS. 19A to 19C illustrate an example of a touch panel.

FIGS. 20A and 20B illustrate an example of a touch panel.

FIGS. 21A to 21C illustrate examples of a touch panel.

FIGS. 22A to 22C illustrate examples of a touch panel.

FIGS. 23A to 23G illustrate examples of electronic devices and lightingdevices.

FIGS. 24A to 24I illustrate examples of electronic devices.

FIGS. 25A to 25C are photographs and diagrams illustrating a bendingtest.

FIG. 26 illustrates a bent portion.

FIGS. 27A to 27C show results of a bending test and a preservation test.

FIGS. 28A to 28C show results of a bending test and a preservation test.

FIGS. 29A and 29B are photographs of a bend tester.

FIGS. 30A and 30B illustrate an apparatus used for a peeling test and astructure example of a sample, respectively.

FIGS. 31A and 31B show results of TDS analysis and results of examiningpeelability, respectively.

FIGS. 32A and 32B show results of TDS analysis and results of examiningpeelability, respectively.

FIG. 33 shows results of examining peelability.

FIGS. 34A and 34B show results of TDS analysis and results of examiningpeelability, respectively.

FIGS. 35A and 35B show results of TDS analysis and results of examiningpeelability, respectively.

FIGS. 36A and 36B show results of TDS analysis and results of examiningpeelability, respectively.

FIGS. 37A to 37D illustrate a method for manufacturing a light-emittingdevice.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments will be described in detail with reference to drawings. Notethat the present invention is not limited to the description below, andit is easily understood by those skilled in the art that various changesand modifications can be made without departing from the spirit andscope of the present invention. Accordingly, the present inventionshould not be interpreted as being limited to the content of theembodiments below.

Note that in the structures of the invention described below, the sameportions or portions having similar functions are denoted by the samereference numerals in different drawings, and description of suchportions is not repeated. Furthermore, the same hatching pattern isapplied to portions having similar functions, and the portions are notespecially denoted by reference numerals in some cases.

In addition, the position, size, range, or the like of each structureillustrated in drawings and the like is not accurately represented insome cases for easy understanding. Therefore, the disclosed invention isnot necessarily limited to the position, size, range, or the likedisclosed in the drawings and the like.

Embodiment 1

In this embodiment, a light-emitting device of one embodiment of thepresent invention and a manufacturing method thereof will be describedwith reference to FIGS. 1A to 1F, FIGS. 2A to 2E, FIGS. 3A to 3D, andFIGS. 4A to 4E.

A layer to be peeled can be formed over a formation substrate, peeledoff from the formation substrate, and then transferred to anothersubstrate. With this method, for example, a layer to be peeled which isformed over a formation substrate having high heat resistance can betransferred to a substrate having low heat resistance. Therefore, themanufacturing temperature of the layer to be peeled is not limited bythe substrate having low heat resistance. Moreover, the layer to bepeeled can be transferred to a substrate or the like which is morelightweight, thin, or flexible than the formation substrate, whereby avariety of devices such as a semiconductor device, a light-emittingdevice, or a display device can be made lightweight, thin, and flexible.

Furthermore, electronic devices including the variety of devices, suchas television devices, monitors for computers, digital cameras, digitalvideo cameras, digital photo frames, cellular phones, portable gamemachines, portable information terminals, and audio reproducing devices,can be made lightweight, thin, and flexible.

A device that can be manufactured by one embodiment of the presentinvention includes a functional element. Examples of the functionalelement include a semiconductor element such as a transistor; alight-emitting diode; a light-emitting element such as an inorganic ELelement and an organic EL element; and a display element such as aliquid crystal element. For example, a semiconductor device including atransistor and a light-emitting device including a light-emittingelement (here, a display device including a transistor and alight-emitting element is also included) are examples of the device thatcan be manufactured according to one embodiment of the presentinvention.

For example, an organic EL element is likely to deteriorate due tomoisture or the like; therefore, reliability might be insufficient whenthe organic EL element is formed over an organic resin substrate havinga poor moisture-proof property. Here, according to one embodiment of thepresent invention, a protective film having an excellent moisture-proofproperty is formed over a glass substrate at a high temperature, wherebythe protective film can be transferred to a flexible organic resinsubstrate having low heat resistance and a poor moisture-proof property.A highly reliable flexible light-emitting device can be manufactured byforming an organic EL element over the protective film transferred tothe organic resin substrate.

Another example is as follows: after a protective film having anexcellent moisture-proof property is formed over a glass substrate at ahigh temperature and an organic EL element is formed over the protectivefilm, the protective film and the organic EL element can be peeled offfrom the glass substrate and transferred to a flexible organic resinsubstrate having a low heat resistance and a poor moisture-proofproperty. A highly reliable flexible light-emitting device can bemanufactured by transferring the protective film and the organic ELelement to the organic resin substrate.

Here, two methods for manufacturing the device are described briefly.Note that in this embodiment, a method for manufacturing the devicewhich will be described in Embodiment 2 can be referred to asappropriate.

FIGS. 1A to 1F illustrate a method for manufacturing the device in whicha peeling process is performed once.

First, as illustrated in FIG. 1A, an insulating layer 104 (e.g., theabove-described protective film having an excellent moisture-proofproperty) is formed over a formation substrate 101 with a peeling layer103 provided therebetween. If necessary, at least part of an elementlayer 106 (e.g., the above-described organic EL element and thesemiconductor element such as a transistor) is further formed over theinsulating layer 104. Then, the element layer 106 and a substrate 109are attached to each other with a bonding layer 107. Note that theelement layer 106 may be formed partly or entirely before being attachedto the substrate 109 or may be formed over the insulating layer 104after the insulating layer 104 is transferred to a substrate 114.

Next, as illustrated in FIG. 1B, the formation substrate 101 is peeledoff from the insulating layer 104 using the peeling layer 103.

Then, as illustrated in FIG. 1C, the exposed insulating layer 104 isattached to the substrate 114 with a bonding layer 112.

After that, the substrate 109 is removed by dissolving or plasticizingthe bonding layer 107 (FIG. 1D). In FIG. 1E, when it is necessary topartly or entirely form layers of the element layer 106, the elementlayer 106 is formed partly or entirely. For example, the followingstructure may be employed: elements up to a lower electrode of theorganic EL element are formed in the step of FIG. 1A and an EL layer andan upper electrode are formed over the lower electrode in the step ofFIG. 1E to complete the organic EL element. As illustrated in FIG. 1F,the element layer 106 and a substrate 173 are attached to each otherwith a bonding layer 171 after the element layer 106 is formed. In theabove manner, the device of one embodiment of the present invention canbe manufactured.

FIGS. 2A to 2E illustrate a method for manufacturing the device in whicha peeling process is performed twice.

First, an insulating layer 204 (e.g., the above-described protectivefilm having an excellent moisture-proof property) is formed over aformation substrate 201 with a peeling layer 203 provided therebetween.An element layer 206 (e.g., a layer including the above-describedsemiconductor element such as a transistor and the element such as anorganic EL element) is further formed over the insulating layer 204. Inaddition, an insulating layer 224 (e.g., the above-described protectivefilm having an excellent moisture-proof property) is formed over aformation substrate 221 with a peeling layer 223 provided therebetween.Furthermore, a functional layer 226 (e.g., a layer including a coloringlayer, a light-blocking layer, and the like, which may include theabove-described semiconductor element such as a transistor and theelement such as an organic EL element) is formed over the insulatinglayer 224. Then, the sides of the two formation substrates on each ofwhich the peeling layer is formed are faced each other to attach theelement layer 206 and the functional layer 226 each other with a bondinglayer 207 (FIG. 2A).

Next, as illustrated in FIG. 2B, the formation substrate 201 is peeledoff from the insulating layer 204 using the peeling layer 203. Then, asillustrated in FIG. 2C, the exposed insulating layer 204 is attached toa substrate 231 with a bonding layer 233.

Next, as illustrated in FIG. 2D, the formation substrate 221 is peeledoff from the insulating layer 224 using the peeling layer 223. Then, asillustrated in FIG. 2E, the exposed insulating layer 224 is attached tothe substrate 173 with the bonding layer 171. In the above manner, thedevice of one embodiment of the present invention can be manufactured.

In the above two methods for manufacturing the device, a crack (breakingor cracking the layer or the film) might occur in the insulating layer,the element layer, and films (typically an inorganic insulating film) ofthe functional layer at the time of peeling the formation substrate.Even when the crack occurs at the time of peeling is not fatal, thenumber of cracks or their sizes might be increased depending onsubsequent manufacturing steps (e.g., heat treatment), the use of thedevice after manufacture, or the like. The occurrence of a crack in thedevice results in a malfunction of the elements, a reduction oflifetime, and the like and accordingly the reliability of the devicemight be reduced.

Thus, according to one embodiment of the present invention, the hardnessof the bonding layer used for the device is set to be higher than ShoreD of 70. Accordingly, it is possible to suppress occurrence of a crackin the insulating layer, the element layer, and films (typically aninorganic insulating film) of the functional layer at the time ofpeeling the formation substrate. Furthermore, a flexible device to whichthis structure is applied is preferable because of its high resistanceto repeated bending. For example, the device of one embodiment of thepresent invention has a minimum curvature radius when bent, which can begreater than or equal to 0.1 mm and less than or equal to 150 mm,preferably greater than or equal to 1 mm and less than or equal to 100mm, further preferably greater than or equal to 1 mm and less than orequal to 50 mm, or still further preferably greater than or equal to 2mm and less than or equal to 5 mm.

For example, a bonding layer having hardness higher than Shore D of 70may be used for at least any one of the above bonding layers 107, 112,171, 207, and 233. It is preferable that the hardness of each bondinglayer be higher than Shore D of 70.

Alternatively, according to one embodiment of the present invention, thecoefficient of expansion of a flexible substrate used for the device isless than 58 ppm/° C. Accordingly, it is possible to suppress occurrenceof a crack or development of the crack in the insulating layer, theelement layer, the functional layer, and the like after these layers aretransferred to the flexible substrate.

For example, a substrate having a coefficient of expansion less than 58ppm/° C. may be used for at least any one of the above-describedsubstrates 114, 173, and 231. The coefficient of expansion of eachsubstrate is preferably less than 58 ppm/° C.

Specifically, the light-emitting device of one embodiment of the presentinvention includes a first flexible substrate; a second flexiblesubstrate; an element layer between the first flexible substrate and thesecond flexible substrate; an insulating layer between the firstflexible substrate and the element layer; a first bonding layer betweenthe first flexible substrate and the insulating layer; and a secondbonding layer between the second flexible substrate and the elementlayer. The element layer includes a light-emitting element.

In one embodiment of the present invention, the hardness of the firstbonding layer is preferably higher than Shore D of 70, or furtherpreferably higher than or equal to Shore D of 80.

In a similar manner, in one embodiment of the present invention, thehardness of the second bonding layer is preferably higher than Shore Dof 70, or further preferably higher than or equal to Shore D of 80.

Although in one embodiment of the present invention, the hardness ofboth the first bonding layer and the second bonding layer is preferablyhigher than Shore D of 70, or further preferably higher than or equal toShore D of 80, one embodiment of the present invention is not limitedthereto. The hardness of either the first bonding layer or the secondbonding layer may be higher than Shore D of 70. Alternatively, thehardness of both the first bonding layer and the hardness of the secondbonding layer may be lower than or equal to Shore D 70 in some caseswhere, for example, a layer in which a crack occurs easily is not usedfor the element layer or the insulating layer.

In one embodiment of the present invention, the coefficient of expansionof the first flexible substrate is preferably less than 58 ppm/° C., orfurther preferably less than or equal to 30 ppm/° C.

In a similar manner, in one embodiment of the present invention, thecoefficient of expansion of the second flexible substrate is preferablyless than 58 ppm/° C., or further preferably less than or equal to 30ppm/° C.

Although in one embodiment of the present invention, the coefficients ofexpansion of both the first flexible substrate and the second flexiblesubstrate are preferably less than 58 ppm/° C., or further preferablyless than or equal to 30 ppm/° C., one embodiment of the presentinvention is not limited thereto. The coefficient of expansion of eitherthe first flexible substrate or the second flexible substrate may beless than 58 ppm/° C. Alternatively, the coefficient of expansions ofboth the first flexible substrate and the second flexible substrate maybe greater than or equal to 58 ppm/° C. in some cases where, forexample, a layer in which crack occurs easily is not used for theelement layer or the insulating layer.

Specific examples of a light-emitting device using the light-emittingelement to which one embodiment of the present invention is applied aredescribed below.

Specific Example 1

FIG. 3A is a plan view of the light-emitting device, and FIG. 3C is anexample of a cross-sectional view taken along the dashed-dotted lineA1-A2 in FIG. 3A. The light-emitting device in Specific Example 1 is atop-emission light-emitting device using a color filter method. In thisembodiment, the light-emitting device can have a structure in whichsub-pixels of three colors of, for example, red (R), green (G), and blue(B) express one color, a structure in which sub-pixels of four colors ofR, G, B, and white (W) express one color, or the like. The color elementis not particularly limited and colors other than R, G, B, and W may beused. For example, yellow, cyan, magenta, and the like may be used.

The light-emitting device illustrated in FIG. 3A includes alight-emitting portion 804, a driver circuit portion 806, and a flexibleprinted circuit (FPC) 808. Light-emitting elements and transistorsincluded in the light-emitting portion 804 and the driver circuitportion 806 are sealed with a substrate 801, a substrate 803, and abonding layer 823.

The light-emitting device in FIG. 3C includes the substrate 801, abonding layer 811, an insulating layer 813, a plurality of transistors,a conductive layer 857, an insulating layer 815, an insulating layer817, a plurality of light-emitting elements, an insulating layer 821,the bonding layer 823, an overcoat 849, a coloring layer 845, alight-blocking layer 847, an insulating layer 843, a bonding layer 841,and the substrate 803. The bonding layer 823, the overcoat 849, theinsulating layer 843, the bonding layer 841, and the substrate 803transmit visible light.

The light-emitting portion 804 includes a transistor 820 and alight-emitting element 830 over the substrate 801 with the bonding layer811 and the insulating layer 813 provided therebetween. Thelight-emitting element 830 includes a lower electrode 831 over theinsulating layer 817, an EL layer 833 over the lower electrode 831, andan upper electrode 835 over the EL layer 833. The lower electrode 831 iselectrically connected to a source electrode or a drain electrode of thetransistor 820. An end portion of the lower electrode 831 is coveredwith the insulating layer 821. It is preferable that the lower electrode831 reflect visible light. The upper electrode 835 transmits visiblelight.

In addition, the light-emitting portion 804 includes the coloring layer845 overlapping with the light-emitting element 830 and thelight-blocking layer 847 overlapping with the insulating layer 821. Thecoloring layer 845 and the light-blocking layer 847 are covered with theovercoat 849. The space between the light-emitting element 830 and theovercoat 849 is filled with the bonding layer 823.

The insulating layer 815 has an effect of suppressing diffusion ofimpurities to a semiconductor included in the transistor. As theinsulating layer 817, an insulating layer having a planarizationfunction is preferably selected in order to reduce surface unevennessdue to the transistor.

The driver circuit portion 806 includes a plurality of transistors overthe substrate 801 with the bonding layer 811 and the insulating layer813 provided therebetween. In FIG. 3C, one transistor included in thedriver circuit portion 806 is illustrated.

The insulating layer 813 and the substrate 801 are attached to eachother with the bonding layer 811. The insulating layer 843 and thesubstrate 803 are attached to each other with the bonding layer 841. Itis preferable to use films having an excellent moisture-proof propertyas the insulating layer 813 and the insulating layer 843, in which caseentry of an impurity such as moisture into the light-emitting element830 or the transistor 820 can be suppressed, leading to improvedreliability of the light-emitting device.

The conductive layer 857 is electrically connected to an external inputterminal through which a signal (e.g., a video signal, a clock signal, astart signal, a reset signal, or the like) or a potential from theoutside is transmitted to the driver circuit portion 806. Here, anexample in which the FPC 808 is provided as the external input terminalis described. To prevent an increase in the number of manufacturingsteps, the conductive layer 857 is preferably formed using the samematerial and the same step(s) as those of the electrode or the wiring inthe light-emitting portion or the driver circuit portion. Here, anexample is described in which the conductive layer 857 is formed usingthe same material and the same step(s) as those of the electrodes of thetransistor 820.

In the light-emitting device in FIG. 3C, the FPC 808 is located over thesubstrate 803. A connector 825 is connected to the conductive layer 857through an opening provided in the substrate 803, the bonding layer 841,the insulating layer 843, the bonding layer 823, the insulating layer817, and the insulating layer 815. Moreover, the connector 825 isconnected to the FPC 808. The FPC 808 and the conductive layer 857 areelectrically connected to each other with the connector 825 providedtherebetween. In the case where the conductive layer 857 and thesubstrate 803 overlap with each other, the conductive layer 857, theconnector 825, and the FPC 808 are electrically connected to one anotherby forming an opening in the substrate 803 (or using a substrate havingan opening).

In Specific Example 1, it is preferable to employ a bonding layer havinghardness higher than Shore D of 70 for at least any one of the bondinglayers 811, 841, and 823. It is particularly preferable to employ abonding layer having hardness higher than Shore D of 70 for each of thebonding layers 811, 841, and 823. Accordingly, it is possible tosuppress occurrence of a crack in the insulating layer 813, theinsulating layer 843, the transistor, the light-emitting element, andthe like at the time of manufacturing the light-emitting device.Furthermore, the light-emitting device can have high resistance torepeated bending.

Moreover, in Specific Example 1, a substrate having a coefficient ofexpansion less than 58 ppm/° C. is preferably used for at least eitherthe substrate 801 or 803, or further preferably used for both of thesubstrates. Accordingly, it is possible to suppress occurrence of acrack or development of the crack in the insulating layer 813, theinsulating layer 843, the transistor, the light-emitting element, andthe like that are transferred to the substrate 801 and the substrate803. Furthermore, the light-emitting device can have high resistance torepeated bending.

Specific Example 2

FIG. 3B is a plan view of the light-emitting device, and FIG. 3D is anexample of a cross-sectional view taken along the dashed-dotted lineA3-A4 in FIG. 3B. The light-emitting device in Specific Example 2 is atop-emission light-emitting device using a color filter method, whichdiffers from the light-emitting device in Specific Example 1. Here, onlydifferent points from those of Specific Example 1 are described and thedescription of the same points as Specific Example 1 is omitted.

The light-emitting device illustrated in FIG. 3D differs from thelight-emitting device in FIG. 3C in the following points.

The light-emitting device in FIG. 3D includes a spacer 827 over theinsulating layer 821. The spacer 827 can adjust the distance between thesubstrate 801 and the substrate 803.

In addition, in the light-emitting device in FIG. 3D, the substrate 801differs from the substrate 803 in size. The FPC 808 is located over theinsulating layer 843 and does not overlap with the substrate 803. Theconnector 825 is connected to the conductive layer 857 through anopening provided in the insulating layer 843, the bonding layer 823, theinsulating layer 817, and the insulating layer 815. Since it is notnecessary to form the opening in the substrate 803, the material of thesubstrate 803 is not limited.

Specific Example 3

FIG. 4A is a plan view of the light-emitting device, and FIG. 4C is anexample of a cross-sectional view taken along the dashed-dotted lineA5-A6 in FIG. 4A. The light-emitting device in Specific Example 3 is atop-emission light-emitting device using a separate coloring method.

The light-emitting device illustrated in FIG. 4A includes thelight-emitting portion 804, the driver circuit portion 806, and the FPC808. A light-emitting element and transistors included in thelight-emitting portion 804 and the driver circuit portion 806 are sealedwith the substrate 801, the substrate 803, a frame-shaped bonding layer824, and the bonding layer 823.

The light-emitting device in FIG. 4C includes the substrate 801, thebonding layer 811, the insulating layer 813, a plurality of transistors,the conductive layer 857, the insulating layer 815, the insulating layer817, a plurality of light-emitting elements, the insulating layer 821,the bonding layer 823, the frame-shaped bonding layer 824, and thesubstrate 803. The bonding layer 823 and the substrate 803 transmitvisible light.

The frame-shaped bonding layer 824 preferably has a bettermoisture-proof property than the bonding layer 823. Accordingly, entryof an impurity such as moisture into the light-emitting device from theoutside can be suppressed. Thus, the light-emitting device can be highlyreliable.

In Specific Example 3, light emitted from the light-emitting element 830is extracted from the light-emitting device through the bonding layer823. For this reason, the bonding layer 823 preferably has a moreexcellent light-transmitting property than the frame-shaped bondinglayer 824. In addition, the bonding layer 823 preferably has a higherrefractive index than the frame-shaped bonding layer 824. Furthermore,the volume of the bonding layer 823 is preferably less reduced by curingthan that of the frame-shaped bonding layer 824.

The light-emitting portion 804 includes the transistor 820 and thelight-emitting element 830 over the substrate 801 with the bonding layer811 and the insulating layer 813 provided therebetween. Thelight-emitting element 830 includes the lower electrode 831 over theinsulating layer 817, the EL layer 833 over the lower electrode 831, andthe upper electrode 835 over the EL layer 833. The lower electrode 831is electrically connected to the source electrode or the drain electrodeof the transistor 820. The end portion of the lower electrode 831 iscovered with the insulating layer 821. It is preferable that the lowerelectrode 831 reflect visible light. The upper electrode 835 transmitsvisible light.

The driver circuit portion 806 includes a plurality of transistors overthe substrate 801 with the bonding layer 811 and the insulating layer813 provided therebetween. In FIG. 4C, one transistors included in thedriver circuit portion 806 is illustrated.

The insulating layer 813 and the substrate 801 are attached to eachother with the bonding layer 811. It is preferable to use films havingan excellent moisture-proof property as the insulating layer 813, inwhich case entry of an impurity such as moisture into the light-emittingelement 830 or the transistor 820 can be suppressed, leading to improvedreliability of the light-emitting device.

The conductive layer 857 is electrically connected to an external inputterminal through which a signal or a potential from the outside istransmitted to the driver circuit portion 806. Here, an example in whichthe FPC 808 is provided as the external input terminal is described.Here, an example is described in which the conductive layer 857 isformed using the same material and the same step(s) as those of theelectrodes of the transistor 820.

In the light-emitting device in FIG. 4C, the FPC 808 is located over thesubstrate 803. The connector 825 is connected to the conductive layer857 through an opening provided in the substrate 803, the bonding layer823, the insulating layer 817, and the insulating layer 815. Moreover,the connector 825 is connected to the FPC 808. The FPC 808 and theconductive layer 857 are electrically connected to each other with theconnector 825 provided therebetween.

In Specific Example 3, it is preferable to employ a bonding layer havinghardness higher than Shore D of 70 for at least either the bonding layer811 or 823, or further preferably for both of the bonding layers.Accordingly, it is possible to suppress occurrence of a crack in theinsulating layer 813, the transistor, the light-emitting element, andthe like at the time of manufacturing the light-emitting device.Furthermore, the light-emitting device can have high resistance torepeated bending.

Moreover, in Specific Example 3, a substrate having a coefficient ofexpansion less than 58 ppm/° C. is preferably used for at least eitherthe substrate 801 or 803, or further preferably used for both of thesubstrates. Accordingly, it is possible to suppress occurrence of acrack or development of the crack in the insulating layer 813, thetransistor, the light-emitting element, and the like that aretransferred to the substrate 801. Furthermore, the light-emitting devicecan have high resistance to repeated bending.

Specific Example 4

FIG. 4B is a plan view of the light-emitting device, and FIG. 4D is anexample of a cross-sectional view taken along the dashed-dotted lineA7-A8 in FIG. 4B. The light-emitting device in Specific Example 4 is abottom-emission light-emitting device using a color filter method.

The light-emitting device in FIG. 4D includes the substrate 801, thebonding layer 811, the insulating layer 813, a plurality of transistors,the conductive layer 857, the insulating layer 815, the coloring layer845, an insulating layer 817 a, an insulating layer 817 b, a conductivelayer 816, a plurality of light-emitting elements, the insulating layer821, the bonding layer 823, and the substrate 803. The substrate 801,the bonding layer 811, the insulating layer 813, the insulating layer815, the insulating layer 817 a, and the insulating layer 817 b transmitvisible light.

The light-emitting portion 804 includes the transistor 820, a transistor822, and the light-emitting element 830 over the substrate 801 with thebonding layer 811 and the insulating layer 813 provided therebetween.The light-emitting element 830 includes the lower electrode 831 over theinsulating layer 817, the EL layer 833 over the lower electrode 831, andthe upper electrode 835 over the EL layer 833. The lower electrode 831is electrically connected to the source electrode or the drain electrodeof the transistor 820. The end portion of the lower electrode 831 iscovered with the insulating layer 821. It is preferable that the upperelectrode 835 reflect visible light. The lower electrode 831 transmitsvisible light. The location of the coloring layer 845 overlapping withthe light-emitting element 830 is not particularly limited and may be,for example, between the insulating layer 817 a and the insulating layer817 b or between the insulating layer 815 and the insulating layer 817a.

The driver circuit portion 806 includes a plurality of transistors overthe substrate 801 with the bonding layer 811 and the insulating layer813 provided therebetween. In FIG. 4C, two transistors included in thedriver circuit portion 806 is illustrated.

The insulating layer 813 and the substrate 801 are attached to eachother with the bonding layer 811. It is preferable to use films havingan excellent moisture-proof property as the insulating layer 813, inwhich case entry of an impurity such as moisture into the light-emittingelement 830 or the transistors 820 and 822, leading to improvedreliability of the light-emitting device.

The conductive layer 857 is electrically connected to an external inputterminal through which a signal or a potential from the outside istransmitted to the driver circuit portion 806. Here, an example in whichthe FPC 808 is provided as the external input terminal is described.Here, an example is described in which the conductive layer 857 isformed using the same material and the same step(s) as those of theconductive layer 816.

In Specific Example 4, it is preferable to employ a bonding layer havinghardness higher than Shore D of 70 for at least either the bonding layer811 or 823, or further preferably for both of the bonding layers.Accordingly, it is possible to suppress occurrence of a crack in theinsulating layer 813, the transistors, the light-emitting element, andthe like at the time of manufacturing the light-emitting device.Furthermore, the light-emitting device can have high resistance torepeated bending.

Moreover, in Specific Example 4, a substrate having a coefficient ofexpansion less than 58 ppm/° C. is preferably used for at least eitherthe substrate 801 or 803, or further preferably used for both of thesubstrates. Accordingly, it is possible to suppress occurrence of acrack or development of the crack in the insulating layer 813, thetransistors, the light-emitting element, and the like that aretransferred to the substrate 801. Furthermore, the light-emitting devicecan have high resistance to repeated bending.

Specific Example 5

FIG. 4E shows an example of a light-emitting device different from thoseof Specific Examples 1 to 4.

A light-emitting device in FIG. 4E includes the substrate 801, thebonding layer 811, the insulating layer 813, a conductive layer 814, aconductive layer 857 a, a conductive layer 857 b, the light-emittingelement 830, the insulating layer 821, the bonding layer 823, and thesubstrate 803.

The conductive layer 857 a and the conductive layer 857 b, which areexternal connection electrodes of the light-emitting device, can each beelectrically connected to an FPC or the like.

The light-emitting element 830 includes the lower electrode 831, the ELlayer 833, and the upper electrode 835. The end portion of the lowerelectrode 831 is covered with the insulating layer 821. Thelight-emitting element 830 has a bottom emission structure, a topemission structure, or a dual emission structure. The electrode, thesubstrate, the insulating layer, and the like through each of whichlight is extracted transmit visible light. The conductive layer 814 iselectrically connected to the lower electrode 831.

The substrate through which light is extracted may have, as a lightextraction structure, a hemispherical lens, a micro lens array, a filmprovided with an uneven surface structure, a light diffusing film, orthe like. For example, a substrate having the light extraction structurecan be formed by bonding the above lens or film to a resin substratewith an adhesive or the like having substantially the same refractiveindex as the substrate or the lens or film.

The conductive layer 814 is preferably, though not necessarily, providedbecause voltage drop due to the resistance of the lower electrode 831can be suppressed. In addition, for a similar purpose, a conductivelayer electrically connected to the upper electrode 835 may be providedover the insulating layer 821, the EL layer 833, the upper electrode835, or the like.

The conductive layer 814 can be formed to have a single-layer structureor a stacked-layer structure using a material selected from copper,titanium, tantalum, tungsten, molybdenum, chromium, neodymium, scandium,nickel, or aluminum or an alloy material containing any of thesematerials as its main component. The thickness of the conductive layer814 can be greater than or equal to 0.1 μm and less than or equal to 3μm, preferably greater than or equal to 0.1 μm and less than or equal to0.5 μm, for example.

When a paste (e.g., silver paste) is used as a material for theconductive layer electrically connected to the upper electrode 835,metal particles forming the conductive layer aggregate; therefore, thesurface of the conductive layer is rough and has many gaps. Thus, evenwhen the conductive layer is formed over the insulating layer 821, forexample, it is difficult for the EL layer 833 to completely cover theconductive layer; accordingly, the upper electrode and the conductivelayer are electrically connected to each other easily, which ispreferable.

In Specific Example 5, it is preferable to employ a bonding layer havinghardness higher than Shore D of 70 for at least either the bonding layer811 or 823, or further preferably for both of the bonding layers.Accordingly, it is possible to suppress occurrence of a crack in theinsulating layer 813, light-emitting element, and the like at the timeof manufacturing the light-emitting device. Furthermore, thelight-emitting device can have high resistance to repeated bending.

Moreover, in Specific Example 5, a substrate having a coefficient ofexpansion less than 58 ppm/° C. is preferably used for at least eitherthe substrate 801 or 803, or further preferably used for both of thesubstrates. Accordingly, it is possible to suppress occurrence of acrack or development of the crack in the insulating layer 813, thelight-emitting element, and the like that are transferred to thesubstrate 801. Furthermore, the light-emitting device can have highresistance to repeated bending.

<Examples of Materials>

Next, materials and the like that can be used for a light-emittingdevice are described. Note that description on the components alreadydescribed in this specification and the like is omitted in some cases.

As materials for the substrates, glass, quartz, an organic resin, metal,an alloy, or the like can be used. The substrate through which light isextracted from the light-emitting element is formed using a materialwhich transmits the light.

In particular, a flexible substrate is preferably used. For example, anorganic resin, a glass material that is thin enough to have flexibility,metal, or an alloy can be used.

An organic resin, which has a specific gravity smaller than that ofglass, is preferably used for the flexible substrate, in which case thelight-emitting device can be lightweight as compared with the case whereglass is used.

The substrate is preferably formed using a material with high toughness.In that case, a light-emitting device with high impact resistance thatis less likely to be broken can be provided. For example, when anorganic resin substrate or a thin metal or alloy substrate is used, thelight-emitting device can be lightweight and unlikely to be broken ascompared with the case where a glass substrate is used.

A metal material and an alloy material, which have high thermalconductivity, are preferable because they can easily conduct heat to thewhole substrate and accordingly can prevent a local temperature rise inthe light-emitting device. The thickness of a substrate using a metalmaterial or an alloy material is preferably greater than or equal to 10μm and less than or equal to 200 μm, or further preferably greater thanor equal to 20 μm and less than or equal to 50 μm.

There is no particular limitation on a material of the metal substrateor the alloy substrate, but it is preferable to use, for example,aluminum, copper, nickel, a metal alloy such as an aluminum alloy orstainless steel.

Furthermore, when a material with high thermal emissivity is used forthe substrate, the surface temperature of the light-emitting device canbe prevented from rising, leading to prevention of breakage or adecrease in reliability of the light-emitting device. For example, thesubstrate may have a stacked-layer structure of a metal substrate and alayer with high thermal emissivity (the layer can be formed using ametal oxide or a ceramic material, for example).

Examples of such a material having flexibility and a light-transmittingproperty include polyester resins such as polyethylene terephthalate(PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, apolyimide resin, a polymethyl methacrylate resin, a polycarbonate (PC)resin, a polyethersulfone (PES) resin, a polyamide resin, a cycloolefinresin, a polystyrene resin, a polyamide imide resin, and a polyvinylchloride resin. In particular, a material having a low coefficient ofthermal expansion is preferable, and for example, a polyamide imideresin, a polyimide resin, PET, or the like can be suitably used. Asubstrate in which a fibrous body is impregnated with a resin (alsoreferred to as prepreg) or a substrate whose coefficient of thermalexpansion is reduced by mixing an organic resin with an inorganic fillercan also be used.

The flexible substrate may have a stacked-layer structure in which ahard coat layer (such as a silicon nitride layer) by which a surface ofa light-emitting device is protected from damage, a layer (such as anaramid resin layer) which can disperse pressure, or the like is stackedover a layer of any of the above-mentioned materials.

The flexible substrate may be formed by stacking a plurality of layers.When a glass layer is used, a barrier property against water and oxygencan be improved and thus a highly reliable light-emitting device can beprovided.

For example, a flexible substrate in which a glass layer, a bondinglayer, and an organic resin layer are stacked from the side closer to anorganic EL element can be used. The thickness of the glass layer isgreater than or equal to 20 μm and less than or equal to 200 μm, orpreferably greater than or equal to 25 μm and less than or equal to 100μm. With such a thickness, the glass layer can have both a high barrierproperty against water and oxygen and high flexibility. The thickness ofthe organic resin layer is greater than or equal to 10 μm and less thanor equal to 200 μm, or preferably greater than or equal to 20 μm andless than or equal to 50 μm. Providing such an organic resin layeroutside the glass layer, occurrence of a crack or a break in the glasslayer can be suppressed and mechanical strength can be improved. Withthe substrate that includes such a composite material of a glassmaterial and an organic resin, a highly reliable flexible light-emittingdevice can be provided.

As the bonding layer, various curable adhesives such as a reactivecurable adhesive, a thermosetting adhesive, an anaerobic adhesive, and aphoto curable adhesive such as an ultraviolet curable adhesive can beused. Examples of such adhesives include an epoxy resin, an acrylicresin, a silicone resin, a phenol resin, a polyimide resin, an imideresin, a polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB)resin, an ethylene vinyl acetate (EVA) resin, and the like. Inparticular, a material with low moisture permeability, such as an epoxyresin, is preferable. Alternatively, a two-component-mixture-type resinmay be used. Further alternatively, a bonding sheet or the like may beused.

Furthermore, the resin may include a drying agent. For example, asubstance which adsorbs moisture by chemical adsorption, such as anoxide of an alkaline earth metal (e.g., calcium oxide or barium oxide),can be used. Alternatively, a substance that adsorbs moisture byphysical adsorption, such as zeolite or silica gel, may be used. Thedrying agent is preferably included, in which case it can suppress entryof impurities such as moisture into the functional element and canimprove the reliability of the light-emitting device.

In addition, a filler with a high refractive index or a light scatteringmember is mixed into the resin, in which case the efficiency of lightextraction from the light-emitting element can be improved. For example,titanium oxide, barium oxide, zeolite, zirconium, or the like can beused.

There is no particular limitation on the structure of the transistor inthe light-emitting device. For example, a forward staggered transistoror an inverted staggered transistor may be used. Furthermore, a top-gatetransistor or a bottom-gate transistor may be used. A semiconductormaterial used for the transistors is not particularly limited, and forexample, silicon, germanium, or the like can be used. Alternatively, anoxide semiconductor containing at least one of indium, gallium, andzinc, such as an In—Ga—Zn-based metal oxide, may be used.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. It is preferable that a semiconductorhaving crystallinity be used, in which case deterioration of thetransistor characteristics can be suppressed.

For stable characteristics of the transistor, a base film is preferablyprovided. The base film can be formed to have a single-layer structureor a stacked-layer structure using an inorganic insulating film such asa silicon oxide film, a silicon nitride film, a silicon oxynitride film,or a silicon nitride oxide film. The base film can be formed by asputtering method, a chemical vapor deposition (CVD) method (e.g., aplasma CVD method, a thermal CVD method, or a metal organic CVD (MOCVD)method), an atomic layer deposition (ALD) method, a coating method, aprinting method, or the like. Note that the base film is not necessarilyprovided if not necessary. In each of the above structure examples, theinsulating layer 813 can serve as a base film of the transistor.

As the light-emitting element, a self-luminous element can be used, andan element whose luminance is controlled by current or voltage isincluded in the category of the light-emitting element. For example, alight-emitting diode (LED), an organic EL element, an inorganic ELelement, or the like can be used.

The light-emitting element may have any of a top emission structure, abottom emission structure, and a dual emission structure. A conductivefilm that transmits visible light is used as the electrode through whichlight is extracted. A conductive film that reflects visible light ispreferably used as the electrode through which light is not extracted.

The conductive film that transmits visible light can be formed using,for example, indium oxide, indium tin oxide (ITO), indium zinc oxide,zinc oxide, or zinc oxide to which gallium is added. Alternatively, afilm of a metal material such as gold, silver, platinum, magnesium,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,or titanium; an alloy containing any of these metal materials; a nitrideof any of these metal materials (e.g., titanium nitride); or the likecan be formed thin so as to have a light-transmitting property.Alternatively, a stacked film of any of the above materials can be usedas the conductive film. For example, a stacked film of ITO and an alloyof silver and magnesium is preferably used, in which case conductivitycan be increased. Further alternatively, graphene or the like may beused.

For the conductive film that reflects visible light, for example, ametal material such as aluminum, gold, platinum, silver, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or analloy containing any of these metal materials can be used. In addition,lanthanum, neodymium, germanium, or the like may be added to the metalmaterial or the alloy. Moreover, an alloy containing aluminum (analuminum alloy) such as an alloy of aluminum and titanium, an alloy ofaluminum and nickel, or an alloy of aluminum and neodymium; or an alloycontaining silver such as an alloy of silver and copper, an alloy ofsilver, copper, and palladium, or an alloy of silver and magnesium canbe used for the conductive film. An alloy of silver and copper ispreferable because of its high heat resistance. Furthermore, when ametal film or a metal oxide film is stacked on and in contact with analuminum alloy film, oxidation of the aluminum alloy film can besuppressed. Examples of materials for the metal film or the metal oxidefilm include titanium and titanium oxide. Alternatively, the aboveconductive film that transmits visible light and a film containing ametal material may be stacked. For example, a stacked film of silver andITO or a stacked film of an alloy of silver and magnesium and ITO can beused.

Each of the electrodes can be formed by an evaporation method or asputtering method. Alternatively, a discharging method such as an inkjetmethod, a printing method such as a screen printing method, or a platingmethod may be used.

When a voltage higher than the threshold voltage of the light-emittingelement is applied between the lower electrode 831 and the upperelectrode 835, holes are injected to the EL layer 833 from the anodeside and electrons are injected to the EL layer 833 from the cathodeside. The injected electrons and holes are recombined in the EL layer833 and a light-emitting substance contained in the EL layer 833 emitslight.

The EL layer 833 includes at least a light-emitting layer. In additionto the light-emitting layer, the EL layer 833 may further include one ormore layers containing any of a substance with a high hole-injectionproperty, a substance with a high hole-transport property, ahole-blocking material, a substance with a high electron-transportproperty, a substance with a high electron-injection property, asubstance with a bipolar property (a substance with a high electron- andhole-transport property), and the like.

For the EL layer 833, either a low molecular compound or a highmolecular compound can be used, and an inorganic compound may also beused. Each of the layers included in the EL layer 833 can be formed byany of the following methods: an evaporation method (including a vacuumevaporation method), a transfer method, a printing method, an inkjetmethod, a coating method, and the like.

The light-emitting element is preferably provided between a pair ofinsulating films having an excellent moisture-proof property. In thatcase, entry of an impurity such as moisture into the light-emittingelement can be suppressed, leading to suppressing of a decrease in thereliability of the light-emitting device.

As an insulating film having an excellent moisture-proof property, afilm containing nitrogen and silicon (e.g., a silicon nitride film, asilicon nitride oxide film, or the like), a film containing nitrogen andaluminum (e.g., an aluminum nitride film or the like), or the like canbe used. Alternatively, a silicon oxide film, a silicon oxynitride film,an aluminum oxide film, or the like can be used.

For example, the water vapor transmittance of the insulating film havingan excellent moisture-proof property is lower than or equal to 1×10⁻⁵[g/m²·day], preferably lower than or equal to 1×10⁻⁶ [g/m²·day], furtherpreferably lower than or equal to 1×10⁻⁷ [g/m²·day], or still furtherpreferably lower than or equal to 1×10⁻⁸ [g/m²·day].

The insulating film having an excellent moisture-proof property ispreferably used for the insulating layer 813 or the insulating layer843.

As the insulating layer 815, for example, an inorganic insulating filmsuch as a silicon oxide film, a silicon oxynitride film, or an aluminumoxide film can be used. For example, as the insulating layer 817, theinsulating layer 817 a, and the insulating layer 817 b, an organicmaterial such as polyimide, acrylic, polyamide, polyimide amide, or abenzocyclobutene-based resin can be used. Alternatively, alow-dielectric constant material (a low-k material) or the like can beused. Furthermore, each insulating layer may be formed by stacking aplurality of insulating films.

For the insulating layer 821, an organic insulating material or aninorganic insulating material is used. As the resin, for example, apolyimide resin, a polyamide resin, an acrylic resin, a siloxane resin,an epoxy resin, a phenol resin, or the like can be used. It isparticularly preferable that the insulating layer 821 be formed to havean inclined side wall with continuous curvature, using a photosensitiveresin material.

There is no particular limitation on the method for forming theinsulating layer 821; a photolithography method, a sputtering method, anevaporation method, a droplet discharging method (e.g., an inkjetmethod), a printing method (e.g., a screen printing method, an off-setprinting method, or the like), or the like may be used.

The spacer 827 can be formed using an inorganic insulating material, anorganic insulating material, a metal material, or the like. As theinorganic insulating material and the organic insulating material, forexample, a variety of materials that can be used for the insulatinglayer can be used. As the metal material, titanium, aluminum, or thelike can be used. When the spacer 827 containing a conductive materialis electrically connected to the upper electrode 835, voltage drop dueto the resistance of the upper electrode 835 can be suppressed. Thespacer 827 may have either a tapered shape or an inverse tapered shape.

For example, a conductive layer functioning as an electrode or a wiringof the transistor, an auxiliary electrode of the light-emitting element,or the like, which is used for the light-emitting device, can be formedto have a single-layer structure or a stacked-layer structure using anyof metal materials such as molybdenum, titanium, chromium, tantalum,tungsten, aluminum, copper, neodymium, and scandium, and an alloymaterial containing any of these elements. Alternatively, the conductivelayer may be formed using a conductive metal oxide. As the conductivemetal oxide, indium oxide (e.g., In₂O₃), tin oxide (e.g., SnO₂), zincoxide (ZnO), ITO, indium zinc oxide (e.g., In₂O₃—ZnO), or any of thesemetal oxide materials in which silicon oxide is contained can be used.

The coloring layer is a colored layer that transmits light in a specificwavelength range. For example, a red (R) color filter for transmittinglight in a red wavelength range, a green (G) color filter fortransmitting light in a green wavelength range, a blue (B) color filterfor transmitting light in a blue wavelength range, or the like can beused. Each coloring layer is formed in a desired position with any ofvarious materials by a printing method, an inkjet method, an etchingmethod using a photolithography method, or the like.

The light-blocking layer is provided between the adjacent coloringlayers. The light-blocking layer blocks light emitted from an adjacentlight-emitting element to suppress color mixture between adjacentlight-emitting elements. Here, the coloring layer is provided such thatits end portion overlaps with the light-blocking layer, whereby lightleakage can be reduced. As the light-blocking layer, a material that canblock light from the light-emitting element can be used; for example, ablack matrix may be formed using a resin material containing a metalmaterial, pigment, or dye. Note that it is preferable to provide thelight-blocking layer in a region other than the light-emitting portion,such as a driver circuit portion, in which case undesired leakage ofguided light or the like can be suppressed.

Furthermore, an overcoat covering the coloring layer and thelight-blocking layer may be provided. The overcoat can prevent animpurity and the like contained in the coloring layer from beingdiffused into the light-emitting element. The overcoat is formed with amaterial that transmits light emitted from the light-emitting element;for example, an inorganic insulating film such as a silicon nitride filmor a silicon oxide film, an organic insulating film such as an acrylicfilm or a polyimide film can be used, and further, a stacked-layerstructure of an organic insulating film and an inorganic insulating filmmay be employed.

In the case where upper surfaces of the coloring layer and thelight-blocking layer are coated with a material of the bonding layer, amaterial which has high wettability with respect to the material of thebonding layer is preferably used as the material of the overcoat. Forexample, an oxide conductive film such as an ITO film or a metal filmsuch as an Ag film which is thin enough to transmit light is preferablyused as the overcoat.

For the connector, it is possible to use a paste-like or sheet-likematerial which is obtained by mixture of metal particles and athermosetting resin and for which anisotropic electric conductivity isprovided by thermocompression bonding. As the metal particles, particlesin which two or more kinds of metals are layered, for example, nickelparticles coated with gold are preferably used.

Note that although the light-emitting device including thelight-emitting element is described as an example in this embodiment,one embodiment of the present invention can be applied to variousdevices such as a semiconductor device, a light-emitting device, and adisplay device. Alternatively, one embodiment of the present inventionmay be a device including a touch panel.

In this specification and the like, a display element, a display devicewhich is a device including a display element, a light-emitting element,and a light-emitting device which is a device including a light-emittingelement can employ various modes or can include various elements. Adisplay element, a display device, a light-emitting element, or alight-emitting device includes, for example, at least one of an ELelement (e.g., an EL element including organic and inorganic materials,an organic EL element, or an inorganic EL element), an LED (e.g., awhite LED, a red LED, a green LED, or a blue LED), a transistor (atransistor which emits light depending on current), an electron emitter,a liquid crystal element, electronic ink, an electrophoretic element, agrating light valve (GLV), a plasma display panel (PDP), a displayelement including a micro electro mechanical system (MEMS), a digitalmicromirror device (DMD), a digital micro shutter (DMS), aninterferometric modulator display (IMOD) element, an MEMS shutterdisplay element, optical interference type MEMS display element, anelectrowetting element, a piezoelectric ceramic display, and a displayelement including a carbon nanotube. Other than the above, display mediawhose contrast, luminance, reflectivity, transmittance, or the like ischanged by electrical or magnetic effect may be included. Note thatexamples of a display device having an EL element include an EL displayand the like. Examples of a display device having an electron emitterinclude a field emission display (FED), an SED-type flat panel display(SED: surface-conduction electron-emitter display), and the like.Examples of a display device having a liquid crystal element include aliquid crystal display (e.g., a transmissive liquid crystal display, atransflective liquid crystal display, a reflective liquid crystaldisplay, a direct-view liquid crystal display, or a projection liquidcrystal display) and the like. Examples of a display device havingelectronic ink, ELECTRONIC LIQUID POWDER (registered trademark), or anelectrophoretic element include electronic paper. In the case of atransflective liquid crystal display or a reflective liquid crystaldisplay, some of or all of pixel electrodes function as reflectiveelectrodes. For example, some or all of pixel electrodes are formed tocontain aluminum, silver, or the like. Furthermore, in such a case, amemory circuit such as an SRAM can be provided under the reflectiveelectrodes, leading to lower power consumption.

For example, in this specification and the like, an active matrix methodin which an active element (a non-linear element) is included in a pixelor a passive matrix method in which an active element is not included ina pixel can be used.

In the active matrix method, as an active element, not only a transistorbut also a variety of active elements can be used. For example, a metalinsulator metal (MIM), a thin film diode (TFD), or the like can also beused. Since these elements can be formed with a smaller number ofmanufacturing steps, manufacturing cost can be reduced or a yield can beimproved. Alternatively, since the size of these elements is small, theaperture ratio can be improved, so that power consumption can be reducedor higher luminance can be achieved.

Since an active element is not used in the passive matrix method, thenumber of manufacturing steps is small, so that manufacturing cost canbe reduced or a yield can be improved. Alternatively, since an activeelement is not used, the aperture ratio can be improved, so that powerconsumption can be reduced or higher luminance can be achieved, forexample.

Note that an example of the case where a variety of display is performedusing the display device is shown here; however, one embodiment of thepresent invention is not limited thereto. For example, data is notnecessarily displayed. As an example, the display device may be used asa lighting device. By using the device as a lighting device, it can beused as interior lighting having an attractive design. Alternatively, inone embodiment of the present invention, it can be used as lighting fromwhich light radiates in various directions. Further alternatively, itmay be used as a light source, for example, a backlight, a front light,or the like, not the display device. In other words, it may be used as alighting device for the display panel.

As described in this embodiment, in one embodiment of the presentinvention, the hardness of the bonding layers included in the device isset to be high (specifically, higher than Shore D of 70). Additionally,in one embodiment of the present invention, the coefficient of expansionof the flexible substrate included in the device is set to be small(specifically, less than 58 ppm/° C.), whereby it is possible tosuppress occurrence of a crack in the inorganic insulating film or theelement in the manufacturing process of the device. Moreover, even whena crack occurs in the inorganic insulating film or the element,development of the crack can be suppressed. Accordingly, a device havinghigh reliability and high resistance to repeated bending can beachieved.

This embodiment can be combined with any other embodiment asappropriate.

Embodiment 2

In this embodiment, the peeling method of one embodiment of the presentinvention and a method for manufacturing the device of one embodiment ofthe present invention will be described with reference to FIGS. 5A to5E, FIGS. 6A to 6D, FIGS. 7A, 7B1, 7B2, 7B3, 7B4, 7B5, and 7C, FIGS. 8Ato 8D, FIGS. 9A to 9D, FIGS. 10A to 10D, FIGS. 11A to 11C, FIGS. 12A to12I, FIGS. 13A to 13C, FIGS. 14A to 14C, FIGS. 15A to 15C, FIGS. 16A to16C, FIGS. 17A and 17B, and FIGS. 37A to 37D.

Specifically, one embodiment of the present invention is a peelingmethod including a first step of forming a peeling layer over a firstsubstrate, a second step of forming a layer to be peeled including afirst layer in contact with the peeling layer over the peeling layer, athird step of curing a bonding layer in an overlapping manner with thepeeling layer and the layer to be peeled, a fourth step of removing partof the first layer overlapping with the peeling layer and the bondinglayer to form a peeling starting point, and a fifth step of separatingthe peeling layer and the layer to be peeled. Note that a sheet-likeadhesive is used for the bonding layer.

According to one embodiment of the present invention, in a region wherethe peeling layer, the layer to be peeled, and the bonding layer in thecured state overlap with one another, part of the first layer (a layerwhich is included in the layer to be peeled and which is in contact withthe peeling layer) is removed to form the peeling starting point. Yieldof the peeling can be improved by forming the peeling starting point inthe above region.

Here, when the formation substrate 101 and the substrate 109 areattached to each other using a bonding layer 111 without overlappingwith the peeling layer 103 as in a region surrounded by a dotted line inthe cross-sectional view of FIG. 6A, yield of a subsequent peelingprocess might be decreased depending on a degree of adhesion between theformation substrate 101 and the substrate 109 (or adhesion between alayer over the formation substrate 101 and a layer over the substrate109, which are in contact with the bonding layer 111). FIG. 6Aillustrates a plan view from the substrate 109 side and across-sectional view taken along the dashed-dotted line A1-A2 in theplan view (the substrate 109 is not illustrated in the plan view).

Therefore, in one embodiment of the present invention, a sheet-likeadhesive is preferably used for the bonding layer 111. The sheet-likeadhesive has low fluidity and therefore can be disposed only in adesired region. Thus, the bonding layer can be inhibited from spreadingoutside the peeling layer and a decrease in the yield of the peelingprocess can be suppressed.

When a material having high fluidity is used for the bonding layer, thematerial that protrudes from the desired region is wasted and it takestime to remove the protrusion, for example. The sheet-like adhesive ispreferably used, in which case the cost of the material and the timeneeded to manufacture the device can be reduced.

In the case where the device of one embodiment of the present inventionincludes a plurality of bonding layers, the sheet-like adhesive may beused for at least one of the bonding layers. In particular, it ispreferable to use the sheet-like adhesive for all of the bonding layers.

In the case where the substrate 109 on the side where the peeling layer103 is not provided can be cut by a knife or the like, a cut can be madein the substrate 109, the bonding layer 111, and a layer 105 to bepeeled (hereinafter referred to as a layer 105) (see arrows P2 in FIG.6B). For example, a cut can be made by a sharp knife such as a cutter.Here, an example in which the peeling starting point in a form of asolid line is formed by making a cut in a frame shape in a region wherethe bonding layer 111 and the peeling layer 103 overlap with each otheris shown. With this method, peeling can be performed in a state wherethe layer 105 is peeled easily from the peeling layer 103 even when theadhesion between the formation substrate 101 and the substrate 109 ishigh (FIG. 6C); therefore, a decrease in the yield of the peelingprocess can be suppressed.

However, a method for cutting the substrate 109 and the bonding layer111 has problems in that it takes time, dust is generated, it isdifficult to reuse the formation substrate 101 in which the dust (aremaining portion of the substrate 109 or the bonding layer 111) is lefton the surface, or a sharp knife such as a cutter is worn. Accordingly,cutting the substrate 109 and the bonding layer 111 is not suitable formass production in some cases. The mechanism for improving the yield ofthe peeling in which, for example, a sharp knife or the like is made toslide on the interface of peeling so that the peeling starting point isformed more clearly might be difficult to be applied to mass production.

Therefore, in one embodiment of the present invention, it is preferableto use the sheet-like adhesive for the boding layer to form the peelingstarting point by laser light irradiation. With laser light, thesubstrate does not need to be cut to form the peeling starting point andthus generation of dust can be suppressed, which is preferable. Inaddition, the time taken to form the peeling starting point can beshortened. Moreover, the formation substrate 101 can be reused easilybecause dust that remains on the surface of the formation substrate 101can be reduced. Furthermore, a method using the sheet-like adhesive forthe bonding layer has advantages in that the cost can be reduced and useof the sheet-like adhesive for the bonding layer is easily applied tomass production because a sharp knife such as a cutter is not worn.Peeling can be started by pulling the end portion of any of thesubstrates and therefore can be easily applied to mass production.

Moreover, according to one embodiment of the present invention, in aregion which is in the vicinity of an end portion of the bonding layerin the cured state and in which the peeling layer and the layer to bepeeled overlap with each other, part of the first layer may be removedto form a peeling starting point. In such a case where the peelingstarting point is formed in a position not overlapping with the bondinglayer, it is preferable that the position at which the peeling startingpoint is formed be in a short distance from the bonding layer, wherebythe peeling layer and the layer to be peeled can be separated surely;specifically, it is preferable that the peeling starting point be formedin a distance from the end portion of the bonding layer within 1 mm.

In the above peeling method, the peeling layer and the bonding layerpreferably overlap with each other so that an end portion of the bondinglayer is positioned on an inner side than an end portion of the peelinglayer. When there is a region where the bonding layer does not overlapwith the peeling layer, failure of peeling is likely to occur dependingon the area of the region and adhesion between the bonding layer and alayer in contact therewith. Therefore, it is preferable that the bondinglayer be not positioned on an outer side than the peeling layer. Notethat the end portion of the bonding layer and the end portion of thepeeling layer may overlap with each other.

In the above peeling method, the hardness of the bonding layer in acured state is preferably higher than Shore D of 70, or furtherpreferably higher than or equal to Shore D of 80. Accordingly, it ispossible to suppress occurrence of a crack in the inorganic insulatingfilm or the element in the peeling process. Moreover, even when a crackoccurs in the inorganic insulating film or the element, development ofthe crack can be suppressed. Accordingly, a device having highreliability and high resistance to repeated bending can be achieved.

Two examples of the peeling method of one embodiment of the presentinvention are described below.

<First Peeling Method>

First, the peeling layer 103 is formed over the formation substrate 101,and the layer 105 is formed over the peeling layer 103 (FIG. 5A).Although an example in which the peeling layer is formed to have anisland shape is described here, one embodiment of the present inventionis not limited to such an example. Furthermore, the layer 105 may beformed to have an island shape. In this step, the material of theseparation layer 103 can be selected such that peeling occurs at theinterface between the formation substrate 101 and the peeling layer 103,the interface between the peeling layer 103 and the layer 105, or in thepeeling layer 103 when the layer 105 is peeled off from the formationsubstrate 101. Although an example in which peeling occurs at theinterface between the layer 105 and the peeling layer 103 is describedin this embodiment, one embodiment of the present invention is notlimited to such an example depending on a material used for the peelinglayer 103 or the layer 105. Note that in the case where the layer 105has a stacked-layer structure, a layer in contact with the peeling layer103 is particularly referred to as a first layer.

For example, in the case where the peeling layer 103 has a stacked-layerstructure of a tungsten film and a tungsten oxide film, part of thepeeling layer 103 (here, part of the tungsten oxide film) may remain onthe layer 105 side when peeling occurs at the interface between thetungsten film and the tungsten oxide film (or the vicinity of theinterface). Moreover, the peeling layer 103 remaining on the layer 105side may be removed after peeling. For example, water or an alkalineaqueous solution can be used to remove the tungsten oxide film. Inaddition, for example, a mixture of ammonium water and a hydrogenperoxide solution, a hydrogen peroxide solution, an ethanol aqueoussolution, or the like can be used. Since the rate at which the tungstenoxide film can be removed varies depending on the temperature of wateror a solution, the water or the solution may be selected as appropriate.For example, water at a temperature of approximately 60° C. can removethe tungsten oxide film more easily than water at room temperature.

As the formation substrate 101, a substrate having at least heatresistance high enough to withstand process temperature in amanufacturing process is used. As the formation substrate 101, forexample, a glass substrate, a quartz substrate, a sapphire substrate, asemiconductor substrate, a ceramic substrate, a metal substrate, a resinsubstrate, a plastic substrate, or the like can be used.

Note that it is preferable to use a large-sized glass substrate as theformation substrate 101 in terms of productivity. For example, a glasssubstrate having any of the following sizes or a larger size can beused: the 3rd generation (550 mm×650 mm), the 3.5th generation (600mm×720 mm or 620 mm×750 mm), the 4th generation (680 mm×880 mm or 730mm×920 mm), the 5th generation (1100 mm×1300 mm), the 6th generation(1500 mm×1850 mm), the 7th generation (1870 mm×2200 mm), the 8thgeneration (2200 mm×2400 mm), the 9th generation (2400 mm×2800 mm or2450 mm×3050 mm), and the 10th generation (2950 mm×3400 mm).

In the case where a glass substrate is used as the formation substrate101, as a base film, an insulating film such as a silicon oxide film, asilicon oxynitride film, a silicon nitride film, or a silicon nitrideoxide film is preferably formed between the formation substrate 101 andthe separation layer 103, in which case contamination from the glasssubstrate can be prevented.

The peeling layer 103 can be formed using an element selected fromtungsten, molybdenum, titanium, tantalum, niobium, nickel, cobalt,zirconium, zinc, ruthenium, rhodium, palladium, osmium, iridium, andsilicon; an alloy material containing any of the elements; a compoundmaterial containing any of the elements; or the like. A crystalstructure of a layer containing silicon may be amorphous, microcrystal,or polycrystal. Furthermore, a metal oxide such as aluminum oxide,gallium oxide, zinc oxide, titanium dioxide, indium oxide, indium tinoxide, indium zinc oxide, or an In—Ga—Zn oxide can be used. The peelinglayer 103 is preferably formed using a high-melting point metal materialsuch as tungsten, titanium, or molybdenum, in which case the degree offreedom of the process for forming the layer 105 can be increased.

The peeling layer 103 can be formed by, for example, a sputteringmethod, a plasma CVD method, a coating method (including a spin coatingmethod, a droplet discharging method, a dispensing method, and thelike), a printing method, or the like. The thickness of the peelinglayer 103 is, for example, greater than or equal to 10 nm and less thanor equal to 200 nm, or preferably greater than or equal to 20 nm andless than or equal to 100 nm.

In the case where the peeling layer 103 has a single-layer structure, atungsten layer, a molybdenum layer, or a layer containing a mixture oftungsten and molybdenum is preferably formed. Alternatively, a layercontaining an oxide or an oxynitride of tungsten, a layer containing anoxide or an oxynitride of molybdenum, or a layer containing an oxide oran oxynitride of a mixture of tungsten and molybdenum may be formed.Note that the mixture of tungsten and molybdenum is an alloy of tungstenand molybdenum, for example.

In the case where the peeling layer 103 is formed to have astacked-layer structure including a layer containing tungsten and alayer containing an oxide of tungsten, the layer containing an oxide oftungsten may be formed as follows: the layer containing tungsten isformed first and an insulating film formed of an oxide is formedthereover, so that the layer containing an oxide of tungsten is formedat the interface between the tungsten layer and the insulating film.Alternatively, the layer containing an oxide of tungsten may be formedby performing thermal oxidation treatment, oxygen plasma treatment,nitrous oxide (N₂O) plasma treatment, treatment with a highly oxidizingsolution such as ozone water, or the like on the surface of the layercontaining tungsten. Plasma treatment or heat treatment may be performedin an atmosphere of oxygen, nitrogen, or nitrous oxide alone, or a mixedgas of any of these gasses and another gas. Surface condition of thepeeling layer 103 is changed by the plasma treatment or heat treatment,whereby adhesion between the peeling layer 103 and the insulating layerformed later can be controlled.

Note that the peeling layer is not necessary in the case where peelingat the interface between the formation substrate and the layer to bepeeled is possible. For example, a glass substrate is used as theformation substrate, and an organic resin such as polyimide, polyester,polyolefin, polyamide, polycarbonate, or acrylic is formed in contactwith the glass substrate. Next, adhesion between the formation substrateand the organic resin is improved by laser light irradiation or heattreatment. Then, an insulating film, a transistor, and the like areformed over the organic resin. After that, peeling at the interfacebetween the formation substrate and the organic resin can be performedby performing laser light irradiation with higher energy density higherthan the above laser light irradiation or performing heat treatment at ahigher temperature than the above heat treatment. Moreover, theinterface between the formation substrate and the organic resin may besoaked in a liquid to be separated when peeled.

Since the insulating film, the transistor, and the like are formed overthe organic resin having low heat resistance in the above method, it isimpossible to expose the substrate to high temperatures in themanufacturing process. Here, a manufacturing process at hightemperatures is dispensable for a transistor including an oxidesemiconductor; therefore, the transistor can be favorably formed overthe organic resin.

Note that the organic resin may be used as the substrate of the device.Alternatively, the organic resin may be removed and another substratemay be attached to the exposed surface of the layer to be peeled usingan adhesive.

Alternatively, peeling at the interface between a metal layer and theorganic resin may be performed in the following manner: the metal layeris provided between the formation substrate and the organic resin andcurrent is made to flow in the metal layer so that the metal layer isheated.

There is no particular limitation on a layer formed as the layer 105. Inthis embodiment, an insulating layer over and in contact with thepeeling layer 103 is formed as the layer 105. Furthermore, a functionalelement may be formed over the insulating layer.

The insulating layer over the peeling layer 103 preferably has asingle-layer structure or a stacked-layer structure including any of asilicon nitride film, a silicon oxynitride film, a silicon oxide film, asilicon nitride oxide film, and the like.

The insulating layer can be formed by a sputtering method, a plasma CVDmethod, a coating method, a printing method, or the like. For example,the insulating layer is formed at a temperature higher than or equal to250° C. and lower than or equal to 400° C. by a plasma CVD method,whereby the insulating layer can be a dense film having an excellentmoisture-proof property. Note that the thickness of the insulating layeris preferably greater than or equal to 10 nm and less than or equal to3000 nm, or further preferably greater than or equal to 200 nm and lessthan or equal to 1500 nm.

Next, the layer 105 is attached to a substrate 109 with the bondinglayer 107, and the bonding layer 107 is cured (FIG. 5B). In thisembodiment, a sheet-like adhesive is used for the bonding layer 107.

Here, FIG. 5B corresponds to a cross-sectional view taken along thedashed-dotted line C1-C2 in FIG. 7A. Note that FIG. 7A is a plan viewviewed from the substrate 109 side (the substrate 109 is not illustratedin the plan view).

The bonding layer 107 is provided so that it overlaps with the peelinglayer 103 and the layer 105. As illustrated in FIG. 7A, it is preferablethat an end portion of the bonding layer 107 be not positioned on anouter side than an end portion of the peeling layer 103. When there is aregion where the bonding layer 107 does not overlap with the peelinglayer 103, failure of peeling is likely to occur depending on the areaof the region and adhesion between the bonding layer 107 and a layer incontact therewith. Therefore, it is preferable that the bonding layer107 be positioned on an inner side than the peeling layer 103 or the endportion of the bonding layer 107 and the end portion of the peelinglayer 103 overlap with each other.

In one embodiment of the present invention, a sheet-like adhesive isused for the bonding layer 107. The sheet-like adhesive has low fluidityand therefore can be disposed only in a desired region. Thus, thebonding layer 107 can be inhibited from spreading outside the peelinglayer 103 and a decrease in the yield of the peeling process can besuppressed. Thus, the yield of the peeling process can be improved.

As illustrated in FIG. 6D, a resin layer 113 may be provided outside thebonding layer 107. FIG. 6D illustrates a plan view from the substrate109 side and a cross-sectional view taken along the dashed-dotted lineB1-B2 in the plan view (the substrate 109 is not illustrated in the planview). With the resin layer 113, entry of impurities such as moistureinto the layer 105 can be suppressed even when the light-emitting deviceis exposed to an air atmosphere during the manufacturing process.

Note that the layer 105 and the substrate 109 are preferably attached toeach other in a reduced-pressure atmosphere.

For the sheet-like adhesive, a material having fluidity low enough todispose the material only in a desired region may be used. For example,an optical clear adhesive (OCA) film can be preferably used. Inaddition, various curable bonding sheets using a reactive curableadhesive, a thermosetting adhesive, an anaerobic adhesive, and a photocurable adhesive such as an ultraviolet curable adhesive; an adhesivesheet; a sheet-like or film-like adhesive; or the like can be used.Examples of such adhesives include an epoxy resin, an acrylic resin, asilicone resin, a phenol resin, a polyimide resin, an imide resin, apolyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin, anethylene vinyl acetate (EVA) resin, and the like. In particular, amaterial with low moisture permeability, such as an epoxy resin, ispreferable. With the thermosetting adhesive, the range of choices forthe material of the substrate 109 is preferably wider than that in thecase of using the photo curable adhesive, in which case the adhesive iscurable regardless of a light-transmitting property of the substrate109.

The sheet-like adhesive may have adhesion before attachment or exhibitadhesion after attachment by heating or light irradiation.

Alternatively, an adhesive with which the substrate 109 and the layer105 can be chemically or physically separated when necessary, such as anadhesive which is soluble in water or a solvent or an adhesive which iscapable of being plasticized upon irradiation of UV light, can be usedas the sheet-like adhesive. For example, a sheet-like adhesive using awater-soluble resin may be applied.

Moreover, in one embodiment of the present invention, an adhesive film,a bonding film, and the like in each of which the sheet-like adhesiveand the substrate are stacked may be used.

As the substrate 109, various substrates that can be used as theformation substrate 101 can be used. Alternatively, a film-like flexiblesubstrate may be used.

As the resin layer 113, various curable adhesives such as a reactivecurable adhesive, a thermosetting adhesive, an anaerobic adhesive, and aphoto curable adhesive such as an ultraviolet curable adhesive can beused. Examples of such adhesives include an epoxy resin, an acrylicresin, a silicone resin, a phenol resin, a polyimide resin, an imideresin, a polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB)resin, an ethylene vinyl acetate (EVA) resin, and the like. Inparticular, a material with low moisture permeability, such as an epoxyresin, is preferable. Alternatively, a two-component-mixture-type resinmay be used.

Furthermore, the resin may include a drying agent. For example, asubstance which adsorbs moisture by chemical adsorption, such as anoxide of an alkaline earth metal (e.g., calcium oxide or barium oxide),can be used. Alternatively, a substance that adsorbs moisture byphysical adsorption, such as zeolite or silica gel, may be used. Thedrying agent is preferably included, in which case it can suppressdeterioration of the functional element due to entry of moisture in theair and can improve the reliability of the device.

Alternatively, an adhesive with which the substrate 109 and the layer105 can be chemically or physically separated when necessary, such as anadhesive which is soluble in water or a solvent or an adhesive which iscapable of being plasticized upon irradiation of UV light, can be usedfor the resin layer 113. For example, a water-soluble resin may be used.

When the resin layer 113 is in a cured state, yield of a subsequentpeeling process might be decreased because of a height of adhesionbetween the formation substrate 101 and the substrate 109. Therefore, atleast part of the resin layer 113 is preferably in a semi-cured state oran uncured state. With the use of a material having high viscosity forthe resin layer 113, an effect of suppressing entry of impurities suchas moisture in the air into the layer 105 can be increased even when theresin layer 113 is in a semi-cured state or an uncured state.

For example, part of the resin layer 113 may be cured in such a mannerthat a light curable resin is used for the resin layer 113 and is partlyirradiated with light. Moreover, part of the resin layer 113 ispreferably cured, so that a space between the formation substrate 101and the substrate 109 and positions thereof can be kept constant even inthe case where the device under manufacture is moved from areduced-pressure atmosphere to an atmospheric pressure atmosphere in asubsequent manufacturing process.

Next, a peeling starting point is formed by laser light irradiation(FIGS. 5B and 5C).

A region where the bonding layer 107 in a cured state, the layer 105,and the peeling layer 103 overlap with one another is irradiated withlaser light (see an arrow P1 in FIG. 5B). Although laser lightirradiation may be performed from either substrate side, it ispreferable to perform laser light irradiation from the formationsubstrate 101 side in which the peeling layer 103 is provided so thatirradiation of the functional element or the like with scattered lightcan be suppressed. Note that a material that transmits the laser lightis used for the substrate on the side where laser light irradiation isperformed.

Part of the first layer can be removed and the peeling starting pointcan be formed by cracking (causing break or crack) at least the firstlayer (a layer which is included in the layer 105 and which is incontact with the peeling layer 103) (see a region surrounded by a dashedline in FIG. 5C). Here, an example in which films of the layer 105 arepartly removed is described. At this time, not only the first layer butalso the peeling layer 103, the bonding layer 107, or another layer ofthe layer 105 may be partly removed. Laser light irradiation enablespart of the films of the layer 105, the peeling layer 103, or thebonding layer 107 to be dissolved, evaporated, or thermally broken.

Enlarged views of a region E surrounded by a dashed-dotted line in FIG.7A are illustrated in FIGS. 7B1, 7B2, 7B3, 7B4, and 7B5. In eachenlarged view, a laser light irradiation region 115 is illustrated as anexample. FIGS. 7B1 to 7B5 all illustrate examples in which a regionwhere the bonding layer 107 in a cured state and the peeling layer 103overlap with each other is irradiated with laser light.

It is preferable that at a peeling process, force of separating thelayer 105 and the peeling layer 103 be concentrated at the peelingstarting point; therefore, it is preferable to form the peeling startingpoint not at the center portion of the bonding layer 107 in a curedstate but in the vicinity of the end portion. It is particularlypreferable to form the peeling starting point in the vicinity of thecorner portion compared to the vicinity of the side portion among thevicinities of the end portion. For example, as illustrated in FIGS. 7B1and 7B3, the laser light irradiation region 115 may be positioned onlyin a region where the bonding layer 107 in a cured state and the peelinglayer 103 overlap with each other. Alternatively, as illustrated inFIGS. 7B2, 7B4, and 7B5, the laser light irradiation region 115 may bepositioned not only in the region where the bonding layer 107 in a curedstate and the peeling layer 103 overlap with each other but also in anoutside region thereof. Note that as illustrated in FIG. 7B5, laserlight irradiation in a state in contact with the side of the bondinglayer 107 is also one mode of laser light irradiation of the regionwhere the bonding layer 107 in a cured state and the peeling layer 103overlaps with each other.

As illustrated in FIGS. 7B3 to 7B5, a peeling starting point ispreferably formed in a form of a dashed line by performing laser lightirradiation discontinuously in the vicinity of the end portion of thebonding layer 107 because peeling is easily performed.

As illustrated in FIG. 7C, a peeling starting point in a form of a solidline or a dashed line may be formed in a frame by performing laser lightirradiation continuously or discontinuously in a region where thebonding layer 107 in a cured state and the peeling layer 103 overlapwith each other.

There is no particular limitation on a laser used to form a peelingstarting point. For example, a continuous wave laser or a pulsedoscillation laser can be used. Note that a condition for laser lightirradiation such as frequency, power density, energy density, or beamprofile is controlled as appropriate in consideration of thicknesses,materials, or the like of the formation substrate 101 and the peelinglayer 103.

Then, the layer 105 and the formation substrate 101 are separated fromeach other from the formed peeling starting point (FIGS. 5D and 5E).Accordingly, the layer 105 can be transferred from the formationsubstrate 101 to the substrate 109. At this time, one of the substratesis preferably fixed to a suction stage or the like. For example, theformation substrate 101 may be fixed to the suction stage to peel thelayer 105 from the formation substrate 101. Alternatively, the substrate109 may be fixed to the suction stage to peel the formation substrate101 from the substrate 109.

For example, the layer 105 and the formation substrate 101 may beseparated by mechanical force (a peeling process with a human hand or agripper, a separation process by rotation of a roller, or the like) fromthe peeling starting point.

The formation substrate 101 and the layer 105 may be separated byfilling the interface between the peeling layer 103 and the layer 105with liquid such as water. A portion between the peeling layer 103 andthe layer 105 absorbs a liquid through capillarity action, so that thepeeling layer 103 can be separated easily. Furthermore, an adverseeffect on the functional element included in the layer 105 due to staticelectricity caused at peeling (e.g., a phenomenon in which asemiconductor element is damaged by static electricity) can besuppressed. Note that liquid can be sprayed in the form of mist orsteam. As the liquid, pure water is preferable, and an organic solventor the like can be used. For example, a neutral solution, an alkalinesolution, an acid solution, a solution into which salt is melted, or thelike may be used. In addition, a mixture of ammonium water and ahydrogen peroxide solution, a hydrogen peroxide solution, or the likemay be used.

Note that after the peeling, the bonding layer 107, the resin layer 113,or the like which does not contribute to attachment between the layer105 and the substrate 109 and which remains over the substrate 109 maybe removed. By such removal, an adverse effect on the functional elementin a subsequent step (e.g., entry of impurities) can be preferablysuppressed. For example, an unnecessary resin can be removed by wiping,cleaning, or the like.

In the peeling method of one embodiment of the present inventiondescribed above, peeling is performed in such a manner that a peelingstarting point is formed by laser light irradiation and then theinterface between the peeling layer 103 and the layer 105 is made in apeelable state. Accordingly, the yield of the peeling process can beimproved.

<Second Peeling Method>

First, the peeling layer 203 is formed over the formation substrate 201,and a layer 205 to be peeled (hereinafter referred to as a layer 205) isformed over the peeling layer 203 (FIG. 8A). In addition, the peelinglayer 223 is formed over the formation substrate 221, and a layer 225 tobe peeled (hereinafter referred to as a layer 225) is formed over thepeeling layer 223 (FIG. 8B).

Next, the formation substrate 201 and the formation substrate 221 areattached to each other with the bonding layer 207 so that the surfaceson which the layers to be peeled are formed face each other, and thebonding layer 207 is cured (FIG. 8C). In this embodiment, a sheet-likeadhesive is used for the bonding layer 207.

Note that the formation substrate 201 and the formation substrate 221are preferably attached to each other in a reduced-pressure atmosphere.

Note that although FIG. 8C illustrates the case where the peeling layer203 and the peeling layer 223 are different in size, peeling layers ofthe same size as illustrated in FIG. 8D may be used.

The bonding layer 207 is provided to overlap with the peeling layer 203,the layer 205, the layer 225, and the peeling layer 223. Then, an endportion of the bonding layer 207 is preferably positioned on an innerside than at least an end portion of either the peeling layer 203 or thepeeling layer 223 (the peeling layer which is desirably peeled first).Accordingly, strong adhesion between the formation substrate 201 and theformation substrate 221 can be suppressed; thus, a decrease in yield ofa subsequent peeling process can be suppressed. The sheet-like adhesiveused in one embodiment of the present invention preferably is preferablebecause it has low fluidity and can be disposed only in a desiredregion.

Next, a peeling starting point is formed by laser light irradiation(FIGS. 9A and 9B).

Either the formation substrate 201 or the formation substrate 221 may bepeeled first. In the case where the peeling layers differ in size, asubstrate over which a larger peeling layer is formed may be peeledfirst or a substrate over which a smaller peeling layer is formed may bepeeled first. In the case where an element such as a semiconductorelement, a light-emitting element, or a display element is formed onlyover one of the substrates, the substrate on the side where the elementis formed may be peeled first or the other substrate may be peeledfirst. Here, an example in which the formation substrate 201 is peeledfirst is described.

A region where the bonding layer 207 in a cured state, the layer 205,and the peeling layer 203 overlap with one another is irradiated withlaser light (see an arrow P3 in FIG. 9A).

Part of the first layer is removed; thus, the peeling starting point canbe formed (see a region surrounded by a dashed line in FIG. 9B). At thistime, not only the first layer but also the peeling layer 203, thebonding layer 207, or another layer included in the layer 205 may bepartly removed.

It is preferable that laser light irradiation be performed from thesubstrate side provided with the peeling layer which is desirablypeeled. In the case where a region where the peeling layer 203 and thepeeling layer 223 overlap with each other is irradiated with laserlight, the formation substrate 201 and the peeling layer 203 can beselectively peeled by cracking only the layer 205 between the layer 205and the layer 225 (see a region surrounded by a dotted line in FIG. 9B).Here, an example in which films of the layer 205 are partly removed isdescribed.

When a peeling starting point is formed in both the layer 205 on thepeeling layer 203 side and the layer 225 on the peeling layer 223 sidein the case where the region where the peeling layer 203 and the peelinglayer 223 overlap with each other is irradiated with laser light, itmight be difficult to selectively peel one of the formation substrates.Therefore, laser light irradiation conditions might be restricted sothat only one of the layers to be peeled is cracked.

At this time, it is preferable that the end portion of the bonding layer207 be positioned on an inner side than the end portion of one of thepeeling layer 203 or the peeling layer 223 and on an outer side than anend portion of the other peeling layer. For example, in FIG. 11A, theend portion of the bonding layer 207 is positioned on an inner side thanthe end portion of the peeling layer 203 and on an outer side than theend portion of the peeling layer 223. With a structure illustrated inFIG. 11A, a peeling starting point can be prevented from being formed inboth the peeling layer 203 and the peeling layer 223 by irradiating onlya region overlapping with the peeling layer 203 but not overlapping withthe peeling layer 223 with laser light (FIGS. 11B and 11C). Therefore,there is preferably a small restrict on the laser light irradiationconditions. Although laser light irradiation may be performed fromeither substrate side at this time, it is preferable to perform laserlight irradiation from the formation substrate 201 side in which thepeeling layer 203 is provided so that irradiation of the functionalelement or the like with scattered light can be suppressed.

Then, the layer 205 and the formation substrate 201 are separated fromeach other from the formed peeling starting point (FIGS. 9C and 9D).Accordingly, the layer 205 can be transferred from the formationsubstrate 201 to the formation substrate 221.

Next, the exposed layer 205 is attached to the substrate 231 with abonding layer 233, and the bonding layer 233 is cured (FIG. 10A). Inthis embodiment, a sheet-like adhesive is used for the bonding layer233.

Note that the layer 205 and the substrate 231 are preferably attached toeach other in a reduced-pressure atmosphere.

Next, a peeling starting point is formed by laser light irradiation(FIGS. 10B and 10C).

A region where the bonding layer 233 in a cured state, the layer 225,and the peeling layer 223 overlap with one another is irradiated withlaser light (see an arrow P4 in FIG. 10B). Part of the first layer isremoved; thus, the peeling starting point can be formed (see a regionsurrounded by a dashed line in FIG. 10C). Here, an example in whichfilms of the layer 225 are partly removed is described. At this time,not only the first layer but also the peeling layer 223, the bondinglayer 233, or another layer included in the layer 225 may be partlyremoved.

It is preferable that laser light irradiation be performed from theformation substrate 221 side in which the peeling layer 223 is provided.

Then, the layer 225 and the formation substrate 221 are separated fromeach other from the formed peeling starting point (FIG. 10D).Accordingly, the layer 205 and the layer 225 can be transferred to thesubstrate 231.

Note that although an example in which a sheet-like adhesive is used forboth the bonding layer 207 and the bonding layer 233 is described above,one embodiment of the present invention is not limited thereto; asheet-like adhesive may be used for one of the bonding layers, forexample.

In addition, although an example in which an end portion of the bondinglayer 233 is positioned on an outer side than an end portion of thebonding layer 207 is illustrated in FIGS. 10A to 10D, one embodiment ofthe present invention is not limited thereto. For example, asillustrated in FIGS. 37A to 37D, the end portion of the bonding layer233 may be positioned on an inner side than the end portion of thebonding layer 207.

In the peeling method of one embodiment of the present inventiondescribed above, peeling is performed in such a manner that a peelingstarting point is formed by laser light irradiation after a pair offormation substrates each provided with a peeling layer and a layer tobe peeled are attached to each other and then the peeling layers andlayers to be peeled are made in a peelable state. Accordingly, the yieldof the peeling process can be improved.

Peeling is performed after the pair of formation substrates eachprovided with the layer to be peeled are attached to each other inadvance, then the substrates of the device which is desirablymanufactured can be attached to each other. Therefore, formationsubstrates having low flexibility can be attached to each other when thelayers to be peeled are attached to each other, whereby alignmentaccuracy at the time of attachment can be improved as compared to thecase where flexible substrates are attached to each other.

<Planar Shapes of Peeling Layer>

The planar shape of the peeling layer used in one embodiment of thepresent invention is not particularly limited. FIGS. 12A to 12F eachillustrate an example of the planar shape of the peeling layer. Examplesof a peeling starting portion are illustrated in FIGS. 12A to 12F. It ispreferable that at a peeling process, force of separating the layer tobe peeled and the peeling layer be concentrated at the peeling startingpoint; therefore, it is preferable to form the peeling starting point inthe vicinity of the corner portion compared to the center portion or theside portion of the peeling layer. Note that peeling may be started at aportion other than a peeling starting portion 117 in each of FIGS. 12Ato 12F.

As illustrated in FIG. 12A, the corner portion of the peeling layer 103may be positioned at the corner portion of the formation substrate 101in the planar shape in the case where peeling is desirably started fromthe corner portion of the formation substrate 101. As illustrated inFIGS. 12B, 12D, 12E, and 12F, the corner portion of the peeling layer103 may be positioned at the side portion of the formation substrate 101in the planar shape in the case where peeling is desirably started fromthe side portion of the formation substrate 101. As illustrated in FIG.12C, the corner portion of the peeling layer 103 may be rounded.

As illustrated in FIG. 12G, an end portion of the layer 105 ispositioned on an inner side than the end portion of the peeling layer103. Accordingly, the yield of the peeling process can be improved. Inthe case where there are a plurality of layers 105, the peeling layer103 may be provided in each layer 105 as illustrated in FIG. 12H or aplurality of layers 105 may be provided over one peeling layer 103 asillustrated in FIG. 12I.

<First Method for Manufacturing Device>

Various devices can be manufactured using the peeling method of oneembodiment of the present invention. An example in which alight-emitting device including a light-emitting element is manufacturedby the peeling method of one embodiment of the present invention isdescribed below. The device that can be manufactured by one embodimentof the present invention is not limited thereto; for example, a deviceincluding another functional element described in Embodiment 1 as anexample can be manufactured.

First, a method for manufacturing the above light-emitting device usingthe first peeling method is described. The above description can bereferred to for materials that can be applied to the componentsdescribed using reference numerals similar to those already described.

Note that the light-emitting devices in Specific Examples 3 to 5 ofEmbodiment 1 can be manufactured in a similar manner by changing thestructure of the layer to be peeled.

First, as illustrated in FIG. 13A, the peeling layer 103, the insulatinglayer 813, the transistor, the insulating layer 815, the conductivelayer 857, and the insulating layer 817 are formed over the formationsubstrate 101 in this order. Next, the lower electrode 831 electricallyconnected to the source electrode or the drain electrode of thetransistor is formed. Then, the insulating layer 821 covering the endportion of the lower electrode 831 and the spacer 827 over theinsulating layer 821 are formed. Here, layers from the insulating layer813 to the spacer 827 correspond to a layer to be peeled.

In addition, as illustrated in FIG. 13B, the bonding layer 107 servingas a peeling adhesive is formed over the substrate 109 serving as atemporary support substrate. At this time, adhesive with which thesubstrate 109 and the layer to be peeled can be chemically or physicallyseparated is used as the peeling adhesive. Although a sheet-likeadhesive is used in this embodiment, one embodiment of the presentinvention is not limited thereto.

Next, the substrate 109 and the formation substrate 101 are attached toeach other with the bonding layer 107, and the peeling layer 107 iscured. Then, a peeling starting point is formed by laser lightirradiation (FIG. 13C). At least part of the insulating layer 813 isremoved; thus, the peeling starting point can be formed. Here, anexample in which the insulating layer 813 and the peeling layer 103 arepartly removed is described. Note that in each of the figuresillustrating the steps of forming the peeling starting point, a regionwhere the peeling starting point is formed is surrounded by a dashedline.

The layer to be peeled and the formation substrate 101 are separatedfrom each other from the formed peeling starting point. Accordingly, thelayer to be peeled can be transferred from the formation substrate 101to the substrate 109 (FIG. 14A).

Next, the insulating layer 813 peeled off from the formation substrate101 and exposed is attached to the substrate 801 with the bonding layer811 (FIG. 14B). Although a sheet-like adhesive is used for the bondinglayer 811 in this embodiment, one embodiment of the present invention isnot limited thereto.

After that, the substrate 109 is removed by dissolving or plasticizingthe bonding layer 107. Then, the bonding layer 107 is removed by water,a solvent, or the like to expose the layer to be peeled (here, thespacer 827 or the like) (FIG. 14C).

In the above manner, the layer to be peeled can be transferred from theformation substrate 101 to the substrate 801.

After that, the EL layer and the upper electrode are formed over thelower electrode 831 and the spacer 827 which are exposed, and thelight-emitting element and the substrate are attached to each other withthe bonding layer (e.g., a sheet-like adhesive). Finally, the FPC isattached to each electrode of an input-output terminal portion with theuse of an anisotropic conductive member. An IC chip or the like may bemounted if necessary. Note that when the flexible substrate warpseasily, the attachment accuracy might deteriorate at the time ofattachment of the FPC or a TCP. Therefore, the manufactured device maybe supported by glass, silicone rubber, or the like at the time ofattachment of the FPC or the TCP. Thus, the electrical connection of theFPC or the TCP to the functional element can be performed surely.

<Second Method for Manufacturing Device>

Next, an example in which a top-emission light-emitting device using acolor filter method in FIGS. 3A and 3C (Specific Example 1) ismanufactured by the peeling method of one embodiment of the presentinvention is described.

Note that the light-emitting device in Specific Example 2 of Embodiment1 can be manufactured in a similar manner by changing the structure ofthe layer to be peeled.

First, as illustrated in FIG. 15A, the peeling layer 203 is formed overthe formation substrate 201, and the insulating layer 813 is formed overthe peeling layer 203. Next, a plurality of transistors (the transistor820 and the like), the conductive layer 857, the insulating layer 815,the insulating layer 817, a plurality of light-emitting elements (thelight-emitting element 830 and the like), and the insulating layer 821are formed over the insulating layer 813. An opening is formed in theinsulating layer 821, the insulating layer 817, and the insulating layer815 to expose the conductive layer 857. Here, an EL layer 862 is formedover the exposed conductive layer 857 with the same material and in thesame process as the EL layer of the light-emitting element, and aconductive layer 864 is formed over the EL layer 862 with the samematerial and in the same process as the upper electrode of thelight-emitting element. Note that the EL layer 862 and the conductivelayer 864 are not necessarily provided. Here, layers from the insulatinglayer 813 to the light-emitting element correspond to a layer to bepeeled.

Moreover, as illustrated in FIG. 15B, the peeling layer 223 is formedover the formation substrate 221, and the insulating layer 843 is formedover the peeling layer 223. Next, the light-blocking layer 847 and thecoloring layer 845 are formed over the insulating layer 843 (FIG. 11B).Note that although not illustrated in FIGS. 15A to 15C, an overcoatcovering the light-blocking layer 847 and the coloring layer 845 may beprovided as illustrated in FIG. 3D. Here, the insulating layer 843, thelight-blocking layer 847, and the coloring layer 845 correspond to alayer to be peeled.

Next, the formation substrate 201 and the formation substrate 221 areattached to each other with the bonding layer 823, and the bonding layer823 is cured. Although a sheet-like adhesive is used for the bondinglayer 823 in this embodiment, one embodiment of the present invention isnot limited thereto. Then, a peeling starting point is formed by laserlight irradiation (FIG. 15C). Here, an example in which the insulatinglayer 813 and the peeling layer 203 are partly removed is described.

Peeling is performed after the pair of formation substrates eachprovided with the layer to be peeled are attached to each other inadvance, then the flexible substrates can be attached to each other.Therefore, formation substrates having low flexibility can be attachedto each other when the layers to be peeled are attached to each other,whereby alignment accuracy at the time of attachment can be improved ascompared to the case where flexible substrates are attached to eachother. Therefore, it can be said that this manufacturing method has highalignment accuracy at the time of attachment of the light-emittingelement and the color filter.

The layer to be peeled and the formation substrate 201 are separatedfrom each other from the formed peeling starting point. Accordingly, thelayer to be peeled can be transferred from the formation substrate 201to the formation substrate 221 (FIG. 16A).

Next, the insulating layer 813 peeled off from the formation substrate201 and exposed is attached to the substrate 801 with the bonding layer811. Although a sheet-like adhesive is used for the bonding layer 811 inthis embodiment, one embodiment of the present invention is not limitedthereto.

Next, a peeling starting point is formed by laser light irradiation(FIG. 16B). Then, the insulating layer 843 and the formation substrate221 are separated from each other from the formed peeling starting point(FIG. 16C).

In the above manner, the layer to be peeled can be transferred from theformation substrate 201 and the formation substrate 221 to the substrate801.

After that, a step of exposing the conductive layer 857 and a step ofattaching the insulating layer 843 and the substrate 803 with thebonding layer 841 are performed. Either step may be performed first.Although a sheet-like adhesive is used for the bonding layer 841 in thisembodiment, one embodiment of the present invention is not limitedthereto.

For example, an opening is formed in the insulating layer 843 and thebonding layer 823 to expose the conductive layer 857. In the case wherethe substrate 803 overlaps with the conductive layer 857, the opening isformed also in the substrate 803 and the bonding layer 841 so that theconductive layer 857 is exposed.

The method for forming the opening is not particularly limited and maybe, for example, a laser ablation method, an etching method, an ion beamsputtering method, or the like. As another method, a cut may be made ina film over the conductive layer 857 with a needle, a sharp knife suchas a cutter, or the like and part of the film may be peeled off byphysical force.

For example, removal of part of the film leads to removal of thesubstrate 803, the bonding layer 841, the insulating layer 843, thebonding layer 823, the EL layer 862, and the conductive layer 864 eachoverlapping with the conductive layer 857 (FIG. 17B). For example, anadhesive roller is pressed to the substrate 803 and the roller is rolledand moved relatively. Alternatively, an adhesive tape may be attached tothe substrate 803 and then peeled. Adhesion between the EL layer 862 andthe conductive layer 864 and adhesion between layers included in the ELlayer 862 are low; therefore, separation occurs at an interface betweenthe EL layer 862 and the conductive layer 864 or in the EL layer 862.Accordingly, a region where the substrate 803, the bonding layer 841,the insulating layer 843, the bonding layer 823, the EL layer 862, orthe conductive layer 864 overlaps with the conductive layer 857 can beremoved selectively. Note that in the case where the EL layer 862 or thelike remains over the conductive layer 857, it may be removed with anorganic solvent or the like. FIG. 18 shows how the insulating layer 843or the like overlapping with the conductive layer 857 is actuallyremoved. As indicated by arrows, the insulating layer 843 or the likecan be partly peeled off.

Note that there is no limitation on a method for removing the layeroverlapping with the conductive layer 857 as long as the conductivelayer 857 can be exposed and can be electrically connected to the FPC808 in subsequent steps. The EL layer 862 or the conductive layer 864does not necessarily overlap with the conductive layer 857. For example,the conductive layer 864 is not necessarily provided in the case whereseparation occurs in the EL layer 862. Moreover, when the EL layer 862and the bonding layer 823 are in contact with each other, for example,materials of the two layers might be mixed or an interface between thelayers might become unclear depending on the materials to be used. Insuch a case, the conductive layer 864 is preferably provided between theEL layer 862 and the bonding layer 823 so as to suppress a reduction ofthe reliability of the light-emitting device.

Finally, the FPC 808 is attached to each electrode (the conductive layer857) of the input-output terminal portion with the use of an anisotropicconductive member (the connector 825). An IC chip or the like may bemounted if necessary.

In the peeling method of one embodiment of the present inventiondescribed above, peeling is performed in such a manner that a peelingstarting point is formed and then the interface between the peelinglayer and the layer to be peeled is made in a peelable state.Accordingly, the yield of the peeling process can be improved. As aresult, the light-emitting device can be manufactured with a high yield.

As described in this embodiment, in one embodiment of the presentinvention, the device is manufactured using a sheet-like adhesive. Thesheet-like adhesive has low fluidity and can be disposed only in adesired region. Thus, the bonding layer can be inhibited from spreadingoutside the peeling layer and a decrease in the yield of the peelingprocess can be suppressed. In addition, it is possible to provide apeeling method and a method for manufacturing the device which hasadvantages in that dust can be reduced, the process time can beshortened, and they are favorable for mass production, for example.

This embodiment can be combined with any other embodiment asappropriate.

Embodiment 3

In this embodiment, a structure of a bendable touch panel will bedescribed with reference to FIGS. 19A to 19C, FIGS. 20A and 20B, FIGS.21A to 21C, and FIGS. 22A to 22C. Note that Embodiment 1 can be referredto for a material of each layer. Although a touch panel including alight-emitting element is described in this embodiment as an example,one embodiment of the present invention is not limited to this example.In one embodiment of the present invention, for example, a touch panelincluding another element described in Embodiment 1 as an example can beformed.

Note that in a manner similar to that described in detail in Embodiment1, a bonding layer having hardness higher than Shore D of 70 and asubstrate having a coefficient of expansion less than 58 ppm/° C. arepreferably applied to the touch panel of this embodiment. Moreover, in amanner similar to that described in detail in Embodiment 2, the touchpanel of this embodiment is preferably manufactured using a sheet-likeadhesive.

Structure Example 1

FIG. 19A is a top view of the touch panel. FIG. 19B is a cross-sectionalview taken along the dashed-dotted line A-B and dashed-dotted line C-Din FIG. 19A. FIG. 19C is a cross-sectional view taken along thedashed-dotted line E-F in FIG. 19A.

A touch panel 390 includes a display portion 301 as illustrated in FIG.19A.

The display portion 301 includes a plurality of pixels 302 and aplurality of imaging pixels 308. The imaging pixels 308 can sense atouch of a finger or the like on the display portion 301. Thus, a touchsensor can be formed using the imaging pixels 308.

Each of the pixels 302 includes a plurality of sub-pixels (e.g., asub-pixel 302R). In addition, in the sub-pixels, light-emitting elementsand pixel circuits that can supply electric power for driving thelight-emitting elements are provided.

The pixel circuits are electrically connected to wirings through whichselection signals are supplied and wirings through which image signalsare supplied.

Furthermore, the touch panel 390 is provided with a scan line drivercircuit 303 g(1) that can supply selection signals to the pixels 302 andan image signal line driver circuit 303 s(1) that can supply imagesignals to the pixels 302.

The imaging pixels 308 include photoelectric conversion elements andimaging pixel circuits that drive the photoelectric conversion elements.

The imaging pixel circuits are electrically connected to wirings throughwhich control signals are supplied and wirings through which powersupply potentials are supplied.

Examples of the control signal include a signal for selecting an imagingpixel circuit from which a recorded imaging signal is read, a signal forinitializing an imaging pixel circuit, a signal for determining the timeit takes for an imaging pixel circuit to sense light, and the like.

The touch panel 390 is provided with an imaging pixel driver circuit 303g(2) that can supply control signals to the imaging pixels 308 and animaging signal line driver circuit 303 s(2) that reads out imagingsignals.

The touch panel 390 includes a substrate 510 and a substrate 570 facingthe substrate 510 as illustrated in FIG. 19B.

Flexible materials can be favorably used for the substrate 510 and thesubstrate 570.

Materials with which unintended passage of impurities is inhibited canbe favorably used in the substrate 510 and the substrate 570. Forexample, materials with a vapor permeability lower than or equal to 10⁻⁵g/m²·day, or preferably lower than or equal to 10⁻⁶ g/m²·day can befavorably used.

The substrate 510 can be favorably formed using a material having acoefficient of linear expansion which is substantially equal to that ofthe substrate 570. For example, the coefficient of linear expansion ofthe materials are preferably lower than or equal to 1×10⁻³/K, furtherpreferably lower than or equal to 5×10⁻⁵/K, or still further preferablylower than or equal to 1×10⁻⁵/K.

The substrate 510 is a stacked body including a flexible substrate 510b, an insulating layer 510 a that prevents diffusion of unintentionalimpurities to light-emitting elements, and a bonding layer 510 c thatattaches the insulating layer 510 a to the flexible substrate 510 b.

The substrate 570 is a stacked body including a flexible substrate 570b, an insulating layer 570 a that prevents diffusion of unintentionalimpurities to the light-emitting elements, and a bonding layer 570 cthat attaches the insulating layer 570 a to the flexible substrate 570b.

For example, materials that include polyester, polyolefin, polyamide(e.g., nylon or aramid), polyimide, polycarbonate, or a resin having anacrylic bond, an urethane bond, an epoxy bond, or a siloxane bond can beused for the bonding layer.

A bonding layer 560 attaches the substrate 570 to the substrate 510. Thebonding layer 560 has a refractive index higher than that of the air.The pixel circuits and the light-emitting elements (e.g., alight-emitting element 350R) are provided between the substrate 510 andthe substrate 570.

Each of the pixels 302 includes the sub-pixel 302R, a sub-pixel 302G anda sub-pixel 302B (see FIG. 19C). The sub-pixel 302R includes alight-emitting module 380R, the sub-pixel 302G includes a light-emittingmodule 380G, and the sub-pixel 302B includes a light-emitting module380B.

For example, the sub-pixel 302R includes the light-emitting element 350Rand the pixel circuit that can supply electric power to thelight-emitting element 350R and includes a transistor 302 t (see FIG.19B). Furthermore, the light-emitting module 380R includes thelight-emitting element 350R and an optical element (e.g., a coloringlayer 367R).

The light-emitting element 350R includes a lower electrode 351R, anupper electrode 352, and an EL layer 353 between the lower electrode351R and the upper electrode 352 (see FIG. 19C).

The EL layer 353 includes a first EL layer 353 a, a second EL layer 353b, and an intermediate layer 354 between the first EL layer 353 a andthe second EL layer 353 b.

The light-emitting module 380R includes the coloring layer 367R on thesubstrate 570. The coloring layer transmits light of a particularwavelength and is, for example, a layer that selectively transmits lightof red, green, or blue color. A region that transmits light emitted fromthe light-emitting element as it is may be provided as well.

The light-emitting module 380R, for example, includes a bonding layer360 that is in contact with the light-emitting element 350R and thecoloring layer 367R.

The coloring layer 367R is positioned in a region overlapping with thelight-emitting element 350R. Accordingly, part of light emitted from thelight-emitting element 350R passes through the bonding layer 360 andthrough the coloring layer 367R and is emitted to the outside of thelight-emitting module 380R as indicated by an arrow in FIG. 19B or 19C.

The touch panel 390 includes a light-blocking layer 367BM on thesubstrate 570. The light-blocking layer 367BM is provided so as tosurround the coloring layer (e.g., the coloring layer 367R).

The touch panel 390 includes an anti-reflective layer 367 p positionedin a region overlapping with the display portion 301. As theanti-reflective layer 367 p, a circular polarizing plate can be used,for example.

The touch panel 390 includes an insulating layer 321. The insulatinglayer 321 covers the transistor 302 t. Note that the insulating layer321 can be used as a layer for planarizing unevenness caused by thepixel circuits. An insulating layer on which a layer that can suppressdiffusion of impurities to the transistor 302 t and the like is stackedcan be used as the insulating layer 321.

The touch panel 390 includes the light-emitting elements (e.g., thelight-emitting element 350R) over the insulating layer 321.

The touch panel 390 includes, over the insulating layer 321, a partition328 that overlaps with an end portion of the lower electrode 351R. Inaddition, a spacer 329 that controls the distance between the substrate510 and the substrate 570 is provided on the partition 328.

The image signal line driver circuit 303 s(1) includes a transistor 303t and a capacitor 303 c. Note that the driver circuit can be formed inthe same process and over the same substrate as those of the pixelcircuits. As illustrated in FIG. 19B, the transistor 303 t may include asecond gate 304 over the insulating layer 321. The second gate 304 maybe electrically connected to a gate of the transistor 303 t, ordifferent potentials may be supplied to these gates. Alternatively, ifnecessary, the second gate 304 may be provided for a transistor 308 t,the transistor 302 t, or the like.

The imaging pixels 308 each include a photoelectric conversion element308 p and an imaging pixel circuit for sensing light received by thephotoelectric conversion element 308 p. The imaging pixel circuitincludes the transistor 308 t.

For example, a PIN photodiode can be used as the photoelectricconversion element 308 p.

The touch panel 390 includes a wiring 311 through which a signal issupplied. The wiring 311 is provided with a terminal 319. Note that anFPC 309(1) through which a signal such as an image signal or asynchronization signal is supplied is electrically connected to theterminal 319. Note that a printed wiring board (PWB) may be attached tothe FPC 309(1).

Transistors formed in the same process can be used as the transistor 302t, the transistor 303 t, the transistor 308 t, and the like.

Gates, sources, and drains of the transistors, and various wirings andelectrodes that form the touch panel can be formed to have asingle-layer structure or a stacked-layer structure using, as amaterial, any of metals such as aluminum, titanium, chromium, nickel,copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten,or an alloy containing any of these metals as its main component. Forexample, a single-layer structure of an aluminum film containingsilicon, a two-layer structure in which an aluminum film is stacked overa titanium film, a two-layer structure in which an aluminum film isstacked over a tungsten film, a two-layer structure in which a copperfilm is stacked over a copper-magnesium-aluminum alloy film, a two-layerstructure in which a copper film is stacked over a titanium film, atwo-layer structure in which a copper film is stacked over a tungstenfilm, a three-layer structure in which a titanium film or a titaniumnitride film, an aluminum film or a copper film, and a titanium film ora titanium nitride film are stacked in this order, a three-layerstructure in which a molybdenum film or a molybdenum nitride film, analuminum film or a copper film, and a molybdenum film or a molybdenumnitride film are stacked in this order, and the like can be given. Notethat a transparent conductive material containing indium oxide, tinoxide, or zinc oxide may be used. Copper containing manganese ispreferably used, in which case the shape can be processed by etchingwith high controllability.

Structure Example 2

FIGS. 20A and 20B are perspective views of a touch panel 505. Note thatFIGS. 20A and 20B illustrate only main components for simplicity. FIGS.21A to 21C are each a cross-sectional view taken along the dashed-dottedline X1-X2 in FIG. 20A.

The touch panel 505 includes a display portion 501 and a touch sensor595 (see FIG. 20B). Furthermore, the touch panel 505 includes thesubstrate 510, the substrate 570, and a substrate 590. Note that thesubstrate 510, the substrate 570, and the substrate 590 each haveflexibility.

The display portion 501 includes the substrate 510, a plurality ofpixels over the substrate 510, and a plurality of wirings 511 throughwhich signals are supplied to the pixels. The plurality of wirings 511are led to a peripheral portion of the substrate 510, and part of theplurality of wirings 511 form a terminal 519. The terminal 519 iselectrically connected to an FPC 509(1).

The substrate 590 includes the touch sensor 595 and a plurality ofwirings 598 electrically connected to the touch sensor 595. Theplurality of wirings 598 are led to a peripheral portion of thesubstrate 590, and part of the plurality of wirings 598 form a terminal.The terminal is electrically connected to an FPC 509(2). Note that inFIG. 20B, electrodes, wirings, and the like of the touch sensor 595provided on the back side of the substrate 590 (the side facing thesubstrate 510) are indicated by solid lines for clarity.

As the touch sensor 595, for example, a capacitive touch sensor can beused. Examples of the capacitive touch sensor are a surface capacitivetouch sensor, a projected capacitive touch sensor, and the like.

Examples of the projected capacitive touch sensor are a self capacitivetouch sensor, a mutual capacitive touch sensor, and the like, whichdiffer mainly in the driving method. The use of a mutual capacitive typeis preferable because multiple points can be sensed simultaneously.

An example of using a projected capacitive touch sensor is describedbelow with reference to FIG. 20B.

Note that a variety of sensors that can sense the closeness or thecontact of a sensing target such as a finger can be used.

The projected capacitive touch sensor 595 includes first electrodes 591and second electrodes 592. The first electrodes 591 are electricallyconnected to any of the plurality of wirings 598, and the secondelectrodes 592 are electrically connected to any of the other wirings598.

The second electrodes 592 each have a shape of a plurality ofquadrangles arranged in one direction with one corner of a quadrangleconnected to one corner of another quadrangle as illustrated in FIGS.20A and 20B.

The first electrodes 591 each have a quadrangular shape and are arrangedin a direction intersecting with the direction in which the secondelectrodes 592 extend.

A wiring 594 electrically connects two first electrodes 591 betweenwhich one of the second electrodes 592 is positioned. The intersectingarea of the one of the second electrodes 592 and the wiring 594 ispreferably as small as possible. Such a structure allows a reduction inthe area of a region where the electrodes are not provided, reducingunevenness in transmittance. As a result, unevenness in luminance oflight transmitted through the touch sensor 595 can be reduced.

Note that the shapes of the first electrodes 591 and the secondelectrodes 592 are not limited to the above-mentioned shapes and can beany of a variety of shapes. For example, a plurality of first electrodeseach having a stripe shape may be provided so that space between twoadjacent first electrodes are reduced as much as possible, and aplurality of second electrodes each having a stripe shape may beprovided so as to intersect the first electrodes with an insulatinglayer sandwiched between the first electrodes and the second electrodes.In that case, two adjacent second electrodes may be spaced apart fromeach other. In that case, it is preferable to provide, between the twoadjacent second electrodes, a dummy electrode which is electricallyinsulated from these electrodes, whereby the area of a region having adifferent transmittance can be reduced.

The touch sensor 595 includes the substrate 590, the first electrodes591 and the second electrodes 592 provided in a staggered arrangement onthe substrate 590, an insulating layer 593 covering the first electrodes591 and the second electrodes 592, and the wiring 594 that electricallyconnects the adjacent first electrodes 591 to each other.

A bonding layer 597 attaches the substrate 590 to the substrate 570 sothat the touch sensor 595 overlaps with the display portion 501 asillustrated in FIG. 20B and FIG. 21A.

The first electrodes 591 and the second electrodes 592 are formed usinga light-transmitting conductive material. As a light-transmittingconductive material, a conductive oxide such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded can be used. Note that a film including graphene may be used aswell. The film including graphene can be formed, for example, byreducing a film containing graphene oxide. As a reducing method, amethod with application of heat or the like can be employed.

The first electrodes 591 and the second electrodes 592 may be formed bydepositing a light-transmitting conductive material on the substrate 590by a sputtering method and then removing an unnecessary portion by avariety of patterning technique such as photolithography.

Examples of a material for the insulating layer 593 are a resin such asacrylic or an epoxy resin, a resin having a siloxane bond, and aninorganic insulating material such as silicon oxide, silicon oxynitride,or aluminum oxide.

Furthermore, openings reaching the first electrodes 591 are formed inthe insulating layer 593, and the wiring 594 electrically connects theadjacent first electrodes 591. A light-transmitting conductive materialcan be favorably used as the wiring 594 because the aperture ratio ofthe touch panel can be increased. Moreover, a material with higherconductivity than the conductivities of the first electrode 591 and thesecond electrode 592 can be favorably used for the wiring 594 becauseelectric resistance can be reduced.

Each of the second electrodes 592 extends in one direction, and thesecond electrodes 592 are provided in the form of stripes.

The wiring 594 intersects with one of the second electrodes 592.

Adjacent first electrodes 591 are provided with one of the secondelectrodes 592 provided therebetween and are electrically connected bythe wiring 594.

Note that the first electrodes 591 are not necessarily arranged in thedirection orthogonal to the one of the second electrodes 592.

The wirings 598 are electrically connected to the first electrodes 591and the second electrodes 592. Part of the wirings 598 serves as aterminal. For the wirings 598, a metal material such as aluminum, gold,platinum, silver, nickel, titanium, tungsten, chromium, molybdenum,iron, cobalt, copper, or palladium or an alloy material containing anyof these metal materials can be used.

Note that an insulating layer covering the insulating layer 593 and thewiring 594 may be provided to protect the touch sensor 595.

Furthermore, a connection layer 599 electrically connects the wirings598 to the FPC 509(2).

As the connection layer 599, any of various anisotropic conductive films(ACF), anisotropic conductive pastes (ACP), or the like can be used.

The bonding layer 597 has a light-transmitting property. For example, athermosetting resin or an ultraviolet curable resin can be used;specifically, a resin such as an acrylic resin, a urethane resin, anepoxy resin, or a resin having a siloxane bond can be used.

The display portion 501 includes a plurality of pixels arranged in amatrix. Each of the pixels includes a display element and a pixelcircuit for driving the display element.

In this embodiment, an example of using a light-emitting element thatemits white light as a display element will be described; however, thedisplay element is not limited to such an element.

For example, light-emitting elements that emit light of different colorsmay be included in sub-pixels so that the light of different colors canbe emitted from the respective sub-pixels.

Structures which are similar to those of the substrate 510, thesubstrate 570, and the bonding layer 560 in Structure Example 1 can beapplied to the substrate 510, the substrate 570, and the sealing layer560 in Structure Example 2.

A pixel includes a sub-pixel 502R, and the sub-pixel 502R includes alight-emitting module 580R.

The sub-pixel 502R includes a light-emitting element 550R and the pixelcircuit that can supply electric power to the light-emitting element550R and includes a transistor 502 t. Furthermore, the light-emittingmodule 580R includes the light-emitting element 550R and an opticalelement (e.g., a coloring layer 567R).

The light-emitting element 550R includes a lower electrode, an upperelectrode, and an EL layer between the lower electrode and the upperelectrode.

The light-emitting module 580R includes the coloring layer 567R on thelight extraction side.

In the case where the bonding layer 560 is provided on the lightextraction side, the bonding layer 560 is in contact with thelight-emitting element 550R and the coloring layer 567R.

The coloring layer 567R is positioned in a region overlapping with thelight-emitting element 550R. Accordingly, part of light emitted from thelight-emitting element 550R passes through the coloring layer 567R andis emitted to the outside of the light-emitting module 580R as indicatedby an arrow in FIG. 21A.

The display portion 501 includes a light-blocking layer 567BM on thelight extraction side. The light-blocking layer 567BM is provided so asto surround the coloring layer (e.g., the coloring layer 567R).

The display portion 501 includes an anti-reflective layer 567 ppositioned in a region overlapping with pixels. As the anti-reflectivelayer 567 p, a circular polarizing plate can be used, for example.

The display portion 501 includes an insulating film 521. The insulatingfilm 521 covers the transistor 502 t. Note that the insulating film 521can be used as a layer for planarizing unevenness caused by the pixelcircuits. A stacked film including a layer that can suppress diffusionof impurities can be used as the insulating film 521. This can suppressa reduction of the reliability of the transistor 502 t or the like bydiffusion of impurities.

The display portion 501 includes the light-emitting elements (e.g., thelight-emitting element 550R) over the insulating film 521.

The display portion 501 includes, over the insulating film 521, apartition 528 that overlaps with an end portion of the lower electrode.In addition, a spacer that controls the distance between the substrate510 and the substrate 570 is provided on the partition 528.

A scan line driver circuit 503 g(1) includes a transistor 503 t and acapacitor 503 c. Note that the driver circuit can be formed in the sameprocess and over the same substrate as those of the pixel circuits.

The display portion 501 includes a wiring 511 through which a signal issupplied. The wiring 511 is provided with a terminal 519. Note that theFPC 509(1) through which a signal such as an image signal or asynchronization signal is supplied is electrically connected to theterminal 519.

Note that a printed wiring board (PWB) may be attached to the FPC509(1).

The display portion 501 includes wirings such as scan lines, signallines, and power supply lines. Any of the various conductive filmsdescribed above can be used as the wirings.

Any of various kinds of transistors can be used in the display portion501. A structure in the case of using bottom-gate transistors in thedisplay portion 501 is illustrated in FIGS. 21A and 21B.

For example, a semiconductor layer containing an oxide semiconductor,amorphous silicon, or the like can be used in the transistor 502 t andthe transistor 503 t illustrated in FIG. 21A.

For example, a semiconductor layer containing polycrystalline siliconthat is obtained by crystallization process such as laser annealing canbe used in the transistor 502 t and the transistor 503 t illustrated inFIG. 21B.

A structure in the case of using top-gate transistors in the displayportion 501 is illustrated in FIG. 21C.

For example, a semiconductor layer including polycrystalline silicon, asingle crystal silicon film that is transferred from a single crystalsilicon substrate, or the like can be used in the transistor 502 t andthe transistor 503 t illustrated in FIG. 21C.

Structure Example 3

FIGS. 22A to 22C are cross-sectional views of a touch panel 505B. Thetouch panel 505B described in this embodiment is different from thetouch panel 505 in Structure Example 2 in that the display portion 501displays received image data on the side where the transistors areprovided and that the touch sensor is provided on the substrate 510 sideof the display portion. Different structures will be described in detailbelow, and the above description is referred to for the other similarstructures.

The coloring layer 567R is positioned in a region overlapping with thelight-emitting element 550R. The light-emitting element 550R illustratedin FIG. 22A emits light to the side where the transistor 502 t isprovided. Accordingly, part of light emitted from the light-emittingelement 550R passes through the coloring layer 567R and is emitted tothe outside of the light-emitting module 580R as indicated by an arrowin FIG. 22A.

The display portion 501 includes the light-blocking layer 567BM on thelight extraction side. The light-blocking layer 567BM is provided so asto surround the coloring layer (e.g., the coloring layer 567R).

The touch sensor 595 is provided on the substrate 510 side of thedisplay portion 501 (see FIG. 22A).

The bonding layer 597 is provided between the substrate 510 and thesubstrate 590 and attaches the touch sensor 595 to the display portion501.

Any of various kinds of transistors can be used in the display portion501. A structure in the case of using bottom-gate transistors in thedisplay portion 501 is illustrated in FIGS. 22A and 22B.

For example, a semiconductor layer containing an oxide semiconductor,amorphous silicon, or the like can be used in the transistor 502 t andthe transistor 503 t illustrated in FIG. 22A.

For example, a semiconductor layer containing polycrystalline silicon orthe like can be used in the transistor 502 t and the transistor 503 tillustrated in FIG. 22B.

A structure in the case of using top-gate transistors in the displayportion 501 is illustrated in FIG. 22C.

For example, a semiconductor layer containing polycrystalline silicon, asingle crystal silicon film that is transferred from a single crystalsilicon substrate, or the like can be used in the transistor 502 t andthe transistor 503 t illustrated in FIG. 22C.

This embodiment can be combined with any other embodiment asappropriate.

Embodiment 4

In this embodiment, electronic devices and lighting devices which can bemanufactured by one embodiment of the present invention will bedescribed with reference to FIGS. 23A to 23G and FIGS. 24A to 24I.

A variety of devices such as a light-emitting device, a display device,and a semiconductor device that can be used for an electronic device ora lighting device can be manufactured with a high yield by oneembodiment of the present invention. Moreover, a flexible electronicdevice or lighting device having high productivity can be manufacturedby one embodiment of the present invention. Furthermore, an electronicdevice or a lighting device having high reliability and high resistanceto repeated bending can be manufactured by one embodiment of the presentinvention.

Examples of electronic devices are television devices (also referred toas TV or television receivers), monitors for computers and the like,cameras such as digital cameras and digital video cameras, digital photoframes, cellular phones (also referred to as portable telephonedevices), portable game machines, portable information terminals, audioplayback devices, large game machines such as pin-ball machines, and thelike.

The device manufactured by one embodiment of the present invention hasflexibility and therefore can be incorporated along a curvedinside/outside wall surface of a house or a building or a curvedinterior/exterior surface of a car.

FIG. 23A illustrates an example of a cellular phone. A cellular phone7400 includes a display portion 7402 incorporated in a housing 7401, anoperation button 7403, an external connection port 7404, a speaker 7405,a microphone 7406, and the like. Note that the cellular phone 7400 ismanufactured using the display device manufactured by one embodiment ofthe present invention for the display portion 7402. According to oneembodiment of the present invention, a highly reliable cellular phonehaving a curved display portion can be provided with a high yield.

When the display portion 7402 of the cellular phone 7400 in FIG. 23A istouched with a finger or the like, data can be input into the cellularphone 7400. Moreover, operations such as making a call and inputting aletter can be performed by touch on the display portion 7402 with afinger or the like.

With the operation button 7403, power ON or OFF can be switched. Inaddition, a variety of images displayed on the display portion 7402 canbe switched; switching a mail creation screen to a main menu screen, forexample.

FIG. 23B is an example of a wrist-watch-type portable informationterminal. A portable information terminal 7100 includes a housing 7101,a display portion 7102, a band 7103, a buckle 7104, an operation button7105, an input/output terminal 7106, and the like.

The portable information terminal 7100 is capable of executing a varietyof applications such as mobile phone calls, e-mailing, reading andediting texts, music reproduction, Internet communication, and acomputer game.

The display surface of the display portion 7102 is bent, and images canbe displayed on the bent display surface. Furthermore, the displayportion 7102 includes a touch sensor, and operation can be performed bytouching the screen with a finger, a stylus, or the like. For example,by touching an icon 7107 displayed on the display portion 7102, anapplication can be started.

With the operation button 7105, a variety of functions such as timesetting, power ON/OFF, ON/OFF of wireless communication, setting andcancellation of manner mode, and setting and cancellation of powersaving mode can be performed. For example, the functions of theoperation button 7105 can be set freely by setting the operation systemincorporated in the portable information terminal 7100.

The portable information terminal 7100 can employ near fieldcommunication that is a communication method based on an existingcommunication standard. In that case, for example, mutual communicationbetween the portable information terminal 7100 and a headset capable ofwireless communication can be performed, and thus hands-free calling ispossible.

Moreover, the portable information terminal 7100 includes theinput/output terminal 7106, and data can be directly transmitted to andreceived from another information terminal via a connector. Chargingthrough the input/output terminal 7106 is possible. Note that thecharging operation may be performed by wireless power feeding withoutusing the input/output terminal 7106.

The display portion 7102 of the portable information terminal 7100includes a light-emitting device manufactured by one embodiment of thepresent invention. According to one embodiment of the present invention,a highly reliable portable information terminal having a curved displayportion can be provided with a high yield.

FIGS. 23C to 23E illustrate examples of a lighting device. Lightingdevices 7200, 7210, and 7220 each include a stage 7201 provided with anoperation switch 7203 and a light-emitting portion supported by thestage 7201.

The lighting device 7200 illustrated in FIG. 23C includes alight-emitting portion 7202 having a wave-shaped light-emitting surface,which is a good-design lighting device.

A light-emitting portion 7212 included in the lighting device 7210 inFIG. 23D has two convex-curved light-emitting portions symmetricallyplaced. Thus, all directions can be illuminated with the lighting device7210 as a center.

The lighting device 7220 illustrated in FIG. 23E includes aconcave-curved light-emitting portion 7222. This is suitable forilluminating a specific range because light emitted from thelight-emitting portion 7222 is collected to the front of the lightingdevice 7220.

The light-emitting portion included in each of the lighting devices7200, 7210, and 7220 are flexible; thus, the light-emitting portion maybe fixed on a plastic member, a movable frame, or the like so that anemission surface of the light-emitting portion can be bent freelydepending on the intended use.

Note that although the lighting device in which the light-emittingportion is supported by the stage is described as an example here, ahousing provided with a light-emitting portion can be fixed on a ceilingor suspended from a ceiling. Since the light-emitting surface can becurved, the light-emitting surface is curved to have a depressed shape,whereby a particular region can be brightly illuminated, or thelight-emitting surface is curved to have a projecting shape, whereby awhole room can be brightly illuminated.

Here, each light-emitting portion includes a light-emitting devicemanufactured by one embodiment of the present invention. According toone embodiment of the present invention, a highly reliable lightingdevice having a curved light-emitting portion can be provided with ahigh yield.

FIG. 23F illustrates an example of a portable display device. A displaydevice 7300 includes a housing 7301, a display portion 7302, operationbuttons 7303, a display portion pull 7304, and a control portion 7305.

The display device 7300 includes a rolled flexible display portion 7302in the cylindrical housing 7301.

The display device 7300 can receive a video signal with the controlportion 7305 and can display the received video on the display portion7302. In addition, a battery is included in the control portion 7305.Moreover, a terminal portion for connecting a connector may be includedin the control portion 7305 so that a video signal or power can bedirectly supplied from the outside with a wiring.

With the operation buttons 7303, power ON/OFF, switching of displayedvideos, and the like can be performed.

FIG. 23G illustrates the display device 7300 in a state where thedisplay portion 7302 is pulled out with the display portion pull 7304.Videos can be displayed on the display portion 7302 in this state.Furthermore, the operation buttons 7303 on the surface of the housing7301 allow one-handed operation. The operation buttons 7303 are providednot in the center of the housing 7301 but on one side of the housing7301 as illustrated in FIG. 23F, which makes one-handed operation easy.

Note that a reinforcement frame may be provided for a side portion ofthe display portion 7302 so that the display portion 7302 has a flatdisplay surface when pulled out.

Note that in addition to this structure, a speaker may be provided forthe housing so that sound is output with an audio signal receivedtogether with a video signal.

The display portion 7302 includes a display device manufactured by oneembodiment of the present invention. According to one embodiment of thepresent invention, a lightweight and highly reliable display device canbe provided with a high yield.

FIGS. 24A to 24C illustrate a foldable portable information terminal310. FIG. 24A illustrates the portable information terminal 310 that isopened. FIG. 24B illustrates the portable information terminal 310 thatis being opened or being folded. FIG. 24C illustrates the portableinformation terminal 310 that is folded. The portable informationterminal 310 is highly portable when folded. The portable informationterminal 310 is highly browsable when opened because of its seamlesslarge display region.

A display panel 312 is supported by three housings 315 joined togetherby hinges 313. By folding the portable information terminal 310 at aconnection portion between two housings 315 with the hinges 313, theportable information terminal 310 can be reversibly changed in shapefrom an opened state to a folded state. A display device manufactured byone embodiment of the present invention can be used for the displaypanel 312. For example, a display device that can be bent with a radiusof curvature of greater than or equal to 1 mm and less than or equal to150 mm can be used.

FIGS. 24D and 24E each illustrate a foldable portable informationterminal 320. FIG. 24D illustrates the portable information terminal 320that is folded so that a display portion 322 is on the outside. FIG. 24Eillustrates the portable information terminal 320 that is folded so thatthe display portion 322 is on the inside. When the portable informationterminal 320 is not used, the portable information terminal 320 isfolded so that a non-display portion 325 faces the outside, whereby thedisplay portion 322 can be prevented from being contaminated or damaged.A display device manufactured by one embodiment of the present inventioncan be used for the display portion 322.

FIG. 24F is a perspective view illustrating an external shape of theportable information terminal 330. FIG. 24G is a top view of theportable information terminal 330. FIG. 24H is a perspective viewillustrating an external shape of a portable information terminal 340.

The portable information terminals 330 and 340 each function as, forexample, one or more of a telephone set, a notebook, an informationbrowsing system, and the like. Specifically, the portable informationterminals 330 and 340 each can be used as a smartphone.

The portable information terminals 330 and 340 can display charactersand image information on its plurality of surfaces. For example, threeoperation buttons 339 can be displayed on one surface (FIGS. 24F and24H). In addition, information 337 indicated by dashed rectangles can bedisplayed on another surface (FIGS. 24G and 24H). Examples of theinformation 337 include notification from a social networking service(SNS), display indicating reception of an e-mail or an incoming call,the title of an e-mail or the like, the sender of an e-mail or the like,the date, the time, remaining battery, and the reception strength of anantenna. Alternatively, the operation buttons 339, an icon, or the likemay be displayed in place of the information 337. Although FIGS. 24F and24G illustrate an example in which the information 337 is displayed atthe top, one embodiment of the present invention is not limited thereto.For example, the information may be displayed on the side as in theportable information terminal 340 in FIG. 24H.

For example, a user of the portable information terminal 330 can see thedisplay (here, the information 337) with the portable informationterminal 330 put in a breast pocket of his/her clothes.

Specifically, a caller's phone number, name, or the like of an incomingcall is displayed in a position that can be seen from above the portableinformation terminal 330. Thus, the user can see the display withouttaking out the portable information terminal 330 from the pocket anddecide whether to answer the call.

A display device manufactured by one embodiment of the present inventioncan be used for a display portion 333 mounted in each of a housing 335of the portable information terminal 330 and a housing 336 of theportable information terminal 340. One embodiment of the presentinvention makes it possible to provide a highly reliable display devicehaving a curved display portion with a high yield.

As in a portable information terminal 345 illustrated in FIG. 24I, datamay be displayed on three or more surfaces. Here, data 355, data 356,and data 357 are displayed on different surfaces.

For a display portion 358 included in a housing 351 of the portableinformation terminal 345, a display device manufactured by oneembodiment of the present invention can be used. One embodiment of thepresent invention makes it possible to provide a highly reliable displaydevice having a curved display portion with a high yield.

This embodiment can be combined with any other embodiment asappropriate.

Example 1

In this example, a plurality of flexible samples which differ in thematerial of a bonding layer were fabricated and crack occurrence waschecked.

[Fabrication of Samples]

A method for fabricating samples of this example is described withreference to FIGS. 13A to 13C and FIGS. 14A to 14C.

First, an approximately 200-nm-thick silicon oxynitride film was formedas a base film (not illustrated) over a glass substrate serving as theformation substrate 101. The silicon oxynitride film was formed by aplasma CVD method under the following conditions: the flow rates of asilane gas and an N₂O gas were 10 sccm and 1200 sccm, respectively, thepower supply was 30 W, the pressure was 22 Pa, and the substratetemperature was 330° C. The base film can also function as an etchingstopper of the glass substrate.

Next, a 30-nm-thick tungsten film serving as the peeling layer 103 wasformed over the base film. The tungsten film was formed by a sputteringmethod under the following conditions: the flow rate of an Ar gas was100 sccm, the power supply was 60 kW, the pressure was 2 Pa, and thesubstrate temperature was 100° C.

Next, dinitrogen monoxide (N₂O) plasma treatment was performed. The N₂Oplasma treatment was performed for 240 seconds under the followingconditions: the flow rate of an N₂O gas was 100 sccm, the power supplywas 500 W, the pressure was 100 Pa, and the substrate temperature was330° C.

Next, a layer to be peeled was formed over the peeling layer 103. Thelayer to be peeled includes the insulating layer 813, the transistors,the conductive layer 857, the insulating layer 815, the insulating layer817, the lower electrode 831, the insulating layer 821, and the spacer827 which are illustrated in FIG. 13A.

The insulating layer 813 was formed by stacking a first siliconoxynitride film, a silicon nitride film, a second silicon oxynitridefilm, a silicon nitride oxide film, and a third silicon oxynitride filmin this order.

Specifically, first, the first silicon oxynitride film was formed to athickness of approximately 600 nm over the peeling layer 103. The firstsilicon oxynitride film was formed by a plasma CVD method under thefollowing conditions: the flow rates of a silane gas and an N₂O gas were75 sccm and 1200 sccm, respectively, the power supply was 120 W, thepressure was 70 Pa, and the substrate temperature was 330° C.

Then, the first silicon oxynitride film was processed into an islandshape by wet etching and the peeling layer 103 was processed into anisland shape by dry etching.

Next, the silicon nitride film was formed to a thickness ofapproximately 200 nm over the first silicon oxynitride film. The siliconnitride film was formed by a plasma CVD method under the followingconditions: the flow rates of a silane gas, an H₂ gas, and an NH₃ gaswere 30 sccm, 800 sccm, and 300 sccm, respectively, the power supply was600 W, the pressure was 60 Pa, and the substrate temperature was 330° C.

Next, the second silicon oxynitride film was formed to a thickness ofapproximately 200 nm over the silicon nitride film. The second siliconoxynitride film was formed by a plasma CVD method under the followingconditions: the flow rates of a silane gas and an N₂O gas were 50 sccmand 1200 sccm, respectively, the power supply was 120 W, the pressurewas 70 Pa, and the substrate temperature was 330° C.

Then, the silicon nitride oxide film was formed to a thickness ofapproximately 140 nm over the second silicon oxynitride film. Thesilicon nitride oxide film was formed by a plasma CVD method under thefollowing conditions: the flow rates of a silane gas, an H₂ gas, an N₂gas, an NH₃ gas, and an N₂O gas were 110 sccm, 800 sccm, 800 sccm, 800sccm, and 70 sccm, respectively, the power supply was 320 W, thepressure was 100 Pa, and the substrate temperature was 330° C.

After that, the third silicon oxynitride film was formed to a thicknessof approximately 100 nm over the silicon nitride oxide film. The thirdsilicon oxynitride film was formed under the same conditions as the basefilm.

After that, heat treatment was performed at 450° C. in a nitrogenatmosphere for one hour.

The stacked-layer structure of the three layers of the tungsten film,the first silicon oxynitride film, and the silicon nitride film and theheat treatment are preferable conditions to perform peeling with a highyield.

The second silicon oxynitride film, the silicon nitride oxide film, andthe third silicon oxynitride film adjust the stress on the entireinsulating layer 813 and function as a moisture-proof layer.

In this way, such inorganic films for forming the peeling layer and theinsulating layer have both peelability and a moisture-proof property,and are preferable for manufacturing a highly reliable flexible device.

As the transistor, a transistor including a c-axis aligned crystallineoxide semiconductor (CAAC-OS) was used. Since the CAAC-OS, which is notamorphous, has few defect states, using the CAAC-OS can improve thereliability of the transistor. Moreover, since the CAAC-OS does not havea grain boundary, stress that is caused by bending a flexible devicedoes not easily make a crack occur in a CAAC-OS film.

A CAAC-OS is a crystalline oxide semiconductor having c-axis alignmentof crystals in a direction substantially perpendicular to the filmsurface. It has been found that oxide semiconductors have a variety ofcrystal structures other than a single-crystal structure. An example ofsuch structures is a nano-crystal (nc) structure, which is an aggregateof nanoscale microcrystals. The crystallinity of a CAAC-OS structure islower than that of a single-crystal structure and higher than that of annc structure.

In this example, a channel-etched transistor including an In—Ga—Zn-basedoxide was used. The transistor was fabricated over a glass substrate ata process temperature lower than 500° C.

In a method for fabricating an element such as a transistor directly onan organic resin such as a plastic substrate, the temperature of theprocess for fabricating the element needs to be lower than theheat-resistant temperature of the organic resin. In this example, theformation substrate is a glass substrate and the peeling layer, which isan inorganic film, has high heat resistance; thus, the transistor can befabricated at a temperature equal to that when a transistor isfabricated over a glass substrate. Thus, the performance and reliabilityof the transistor can be easily secured.

Then, the layer to be peeled is attached to the substrate 109 with thebonding layer 107 (FIG. 13C). The materials of the substrate 109 and thebonding layer 107 differ from sample to sample (see Table 1 below). Thesubstrate 109 in each sample has flexibility.

In each sample except a sample 4, the bonding layer 107 was formed usinga laminator, and the thickness of the bonding layer 107 wasapproximately greater than or equal to 3 μm and approximately less thanor equal to 10 μm. In the sample 4, the bonding layer 107 was formedwith a spin coater, and the thickness of the bonding layer 107 wasapproximately greater than or equal to 10 μm and approximately less thanor equal to 20 μm.

The thickness of the substrate 109 was 125 μm. Note that in the sample4, a UV-curable adhesive film UDT-1025MC (manufactured by DENKA ADTECSCO., LTD) was used as the substrate 109. A thickness of 25 μm of thetotal thickness, 125 μm, corresponds to an adhesive layer.

Next, a peeling starting point was formed by laser light irradiation,and the layer to be peeled and the formation substrate 101 wereseparated from each other (FIG. 13C and FIG. 14A).

After that, an exposed surface of the insulating layer 813 was observed,and crack occurrence was checked.

[Experimental Result]

Table 1 shows kinds of the bonding layers 107 and the substrates 109used in the respective samples and the hardness of each bonding layer107. Furthermore, Table 1 also shows result of crack occurrence which isjudged by observing the surface of the insulating layer 813 afterpeeling. Here, the case where a crack was hardly observed was indicatedby circles (∘), and the case where a number of cracks were observed wasindicated by crosses (x).

TABLE 1 sample 1 sample 2 sample 3 sample 4 sample 5 sample 6 bondingmaterial a material b material c material d material e material f layer107 material two-part curable epoxy-based resin UV curable two-partacrylic- acrylic- curable based based resin epoxy-based adhesive resinlayer hardness shore D of shore D of shore D of shore D of shore D ofJIS K6253 84-86 82.5 82 80 70 E25 degrees substrate 109 Kapton ®500HUDT- Kapton ®500H (DU PONT-TORAY 1025MC (DU PONT-TORAY CO. LTD.) (DENKACO. LTD.) ADTECS CO., LTD.) result of crack ∘ ∘ ∘ ∘ x x occurrencejudged by surface observation

According to the result of surface observation, a number of cracks werefound to occur in the fabricating process in a sample 5 using a materiale having hardness of Shore D of 70 for the bonding layer 107 and asample 6 using a material f having hardness of E25 degrees in accordancewith JIS K6253 which is lower than Shore D of 70. On the other hand, ina sample 1, a sample 2, a sample 3, and the sample 4 using a material a,a material b, a material c, and a material d having hardness higher thanor equal to Shore D of 80, respectively, a fatal crack did not occur inthe fabricating process.

Thus, the hardness of the bonding layer used for the flexiblelight-emitting device of one embodiment of the present invention wasfound to be preferably higher than Shore D of 70, or further preferablyhigher than or equal to Shore D of 80. Accordingly, occurrence of cracksin the fabricating process can be suppressed. Therefore, the yield ofthe light-emitting device can be improved. Additionally, the reliabilityof the light-emitting device can be improved.

Example 2

In this example, a plurality of flexible samples which differ in thematerial of a flexible substrate were fabricated and crack occurrencewas checked.

[Fabrication of Samples]

A method for fabricating samples of this example is described withreference to FIGS. 13A to 13C and FIGS. 14A to 14C.

First, an approximately 200-nm-thick silicon oxynitride film was formedas a base film (not illustrated) over a glass substrate serving as theformation substrate 101. Next, a 30-nm-thick tungsten film serving asthe peeling layer 103 was formed over the base film. Next, dinitrogenmonoxide (N₂O) plasma treatment was performed. Next, a layer to bepeeled was formed over the peeling layer 103. The layer to be peeledincludes the insulating layer 813, the transistors, the conductive layer857, the insulating layer 815, the insulating layer 817, the lowerelectrode 831, the insulating layer 821, and the spacer 827 which areillustrated in FIG. 13A. The insulating layer 813 was formed by stackinga first silicon oxynitride film, a first silicon nitride film, a secondsilicon oxynitride film, a silicon nitride oxide film, and a thirdsilicon oxynitride film in this order. After that, heat treatment wasperformed at 450° C. in a nitrogen atmosphere for one hour. As thetransistor, a transistor including a CAAC-OS was used. In this example,a channel-etched transistor including an In—Ga—Zn-based oxide was used.Since the steps up to here are similar to those of Example 1, thedetailed description is omitted.

Then, the layer to be peeled is attached to the substrate 109 with thebonding layer 107 (FIG. 13C). As the substrate 109 and the bonding layer107, a UV-curable adhesive film and the material d which is awater-soluble resin were used, respectively, in a manner similar to thatof the sample 4 of Example 1.

Next, a peeling starting point was formed by laser light irradiation,and the layer to be peeled and the formation substrate 101 wereseparated from each other (FIG. 13C and FIG. 14A).

After that, the substrate 801 is attached to an exposed surface of theinsulating layer 813 with the bonding layer 811 (FIG. 14B). As thematerial of the bonding layer 811, the material c, a two-part curableepoxy-based resin, which was used for the bonding layer 107 in thesample 3 of Example 1, was used. The material of the substrate 801differs from sample to sample (see Table 2 below).

Next, by removal of the bonding layer 107 and the substrate 109 (FIG.14B), the exposed surface (the surface on which the spacer 827 and thelike are formed as illustrated in FIG. 14C) was observed, and crackoccurrence was checked. As a result of the observation, there was hardlyany crack in each sample.

[Heat Treatment]

The fabricated samples were each heated at 60° C. for one hour. Afterthat, the same surface was observed, and crack occurrence was checked.As for a sample in which a fatal crack (e.g., a large crack, a number ofcracks, or the like) was observed after the heat treatment, theexperiment was terminated at that time and subsequent heat treatment wasnot performed.

Next, the sample in which a crack was hardly observed was heated at 80°C. for one hour. After that, crack occurrence was checked similarly.

Then, the sample in which a crack was hardly observed was still furtherheated at 100° C. for one hour. After that, crack occurrence waschecked.

[Experimental Result]

Table 2 shows kinds and coefficients of expansion of the substrate 801used in respective samples. Furthermore, Table 2 also shows result ofcrack occurrence which is judged by observing the surface of the samplebefore and after the heat treatment. Here, the case where a crack washardly observed was indicated by circles (∘), and the case where anumber of cracks were observed was indicated by crosses (x).

TABLE 2 sample 7 sample 8 sample 9 sample 10 sample 11 sample 12substrate 801 materaial m materaial n materaial o materaial p materaialq materaial r material polyethylene polyethylene polyimide polyimidecyclic olefin polycarbonate terephthalate terephthalate thickness 125100 125 100 100 100 (μm) coefficient  10 13-20  27  58  65  70 ofexpansion (ppm/° C.) crack before ∘ ∘ ∘ ∘ ∘ ∘ occurrence heat judged bytreatment surface at 60° C. ∘ ∘ ∘ ∘ x x observation for 1 hour at 80° C.∘ ∘ ∘ x for 1 hour at 100° C. ∘ ∘ ∘ for 1 hour

According to the result of surface observation after the heat treatment,in a sample 10, a sample 11, and a sample 12 whose coefficients ofexpansion of the substrates 801 were each greater than or equal to 58ppm/° C., a fatal crack was found to occur after the heat treatment at60° C. for one hour or at 80° C. for one hour. On the other hand, in asample 7, a sample 8, and a sample 9 whose coefficients of expansion ofthe substrates 801 were each less than or equal to 27 ppm/° C., a fatalcrack did not occur even after the heat treatment at 100° C. for onehour.

Thus, the coefficient of expansion of the flexible substrate used forthe flexible light-emitting device of one embodiment of the presentinvention was found to be preferably less than 58 ppm/° C., or furtherpreferably less than or equal to 27 ppm/° C. With such a coefficient ofexpansion, occurrence of cracks at the heat treatment can be suppressed.Therefore, the reliability of the light-emitting device can be improved.

Example 3

In this example, the flexible light-emitting device of one embodiment ofthe present invention was fabricated and its reliability was evaluated.

The structure of Specific Example 2 (FIGS. 3B and 3D) described inEmbodiment 1 is applied to the light-emitting device fabricated in thisexample. Description in Embodiment 1 can be referred to for the details.

In this example, the light-emitting device was fabricated by the secondpeeling method described in Embodiment 2.

First, the peeling layer 203 was formed over a glass substrate servingas the formation substrate 201, and the layer 205 was formed over thepeeling layer 203 (FIG. 8A). In addition, the peeling layer 223 wasformed over a glass substrate serving as the formation substrate 221,and the layer 225 was formed over the peeling layer 223 (FIG. 8B). Next,the formation substrate 201 and the formation substrate 221 wereattached to each other so that the surfaces on which the layers to bepeeled are formed face each other (FIG. 8C). Then, the two formationsubstrates were peeled from the respective layers to be peeled, andflexible substrates were attached to the respective layers to be peeled(FIG. 10D). Materials for each of the layers are described below.

A stacked-layer structure of a tungsten film and a tungsten oxide filmthereover was formed as each of the peeling layer 203 and the peelinglayer 223.

The peeling layer having the stacked-layer structure right afterdeposition is not easily peeled; however, by reaction with an inorganicinsulating film by heat treatment, the state of the interface betweenthe peeling layer and the inorganic insulating film is changed to becomebrittle. Then, forming a peeling starting point enables physicalpeeling.

As the layer 205, the insulating layer 813, a transistor, and an organicEL element serving as the light-emitting element 830 were formed. Acolor filter, which corresponds to the coloring layer 845, and the likewere formed as the layer 225.

A structure and a formation method similar to those of the insulatinglayer 813 formed in Example 1 were applied to the insulating layer 813and the insulating layer 843.

As the transistor, a transistor including a CAAC-OS was used. In thisexample, a channel-etched transistor including an In—Ga—Zn-based oxidewas used. The transistor was fabricated over a glass substrate at aprocess temperature lower than 500° C.

In a method for fabricating an element such as a transistor directly onan organic resin such as a plastic substrate, the temperature of theprocess for fabricating the element needs to be lower than the uppertemperature limit of the organic resin. In this example, the formationsubstrate is a glass substrate and the peeling layer, which is aninorganic film, has high heat resistance; thus, the transistor can befabricated at a temperature equal to that when a transistor isfabricated over a glass substrate. Thus, the performance and reliabilityof the transistor can be easily secured.

As the light-emitting element 830, a tandem organic EL element thatincluded a fluorescence-emitting unit including a blue light-emittinglayer and a phosphorescence-emitting unit including a greenlight-emitting layer and a red light-emitting layer was used. Thelight-emitting element 830 is a top-emission light-emitting element. Asthe lower electrode 831 of the light-emitting element 830, an aluminumfilm, a titanium film over the aluminum film, and an ITO film serving asan optical adjustment layer over the titanium film were stacked. Thethickness of the optical adjustment layer was varied depending on thecolor of the pixel. Owing to the combination of a color filter and amicrocavity structure, light with high color purity can be extractedfrom the light-emitting device fabricated in this example.

A 20-μm-thick organic resin film having a coefficient of expansion lessthan or equal to 27 ppm/° C. was used as the substrate 801 and thesubstrate 803.

For the bonding layer 823, the bonding layer 811, and the bonding layer841, a two-part curable epoxy-based resin having hardness of Shore D of82, which is similar to the material c used for the sample 3 of Example1, was used.

FIG. 26 illustrates the light-emitting device fabricated in thisexample. The fabricated light-emitting device had a size of alight-emitting portion (pixel portion) of 3.4 inches diagonal, 540×960×3(RGB) pixels, a pixel pitch of 0.078 mm×0.078 mm, a resolution of 326ppi, and an aperture ratio of 56.9%. The light-emitting device had abuilt-in scan driver (gate driver) and source driver. In addition, thelight-emitting device had a thickness less than or equal to 100 μm and aweight of 2 g.

The fabricated light-emitting device was bent repeatedly whiledisplaying an image. As illustrated in FIG. 26, a bent portion is amiddle portion of the light-emitting device and includes thelight-emitting portion (Display Area) and the scan driver (Scan Driver).FIG. 25A is a photograph showing a bend tester where the light-emittingdevice is set. FIG. 25B shows how a bending test is performed. Fixingthe side where an FPC is provided allows the bending test to beperformed while the light-emitting device is driven. As illustrated inFIG. 25C, the radius of curvature for bending a light-emitting device 99was determined by the diameter of a metal rod 98. Four rods withdiameters of 10 mm, 6 mm, 4 mm, and 2 mm were used as the rod 98. Inother words, four bending tests with radiuses of curvature of 5 mm, 3mm, 2 mm, and 1 mm were performed on the light-emitting device. Notethat here, “outward bending” means bending performed such that a displaysurface of the light-emitting device faces outward, and “inward bending”means bending performed such that a display surface faces inward. FIG.25B shows states during an inward bending test. In the bending test, onebending was performed in approximately 2 seconds. In the case where theradius of curvature was 5 mm, the display portion had no defect and thedriver operated normally after either outward bending or inward bendingperformed 100,000 times. When inward bending with a radius of curvatureof 3 mm was performed 100,000 times, the display portion had no defectand the driver operated normally. When inward bending with a radius ofcurvature of 2 mm was performed 100,000 times, the display portion hadno defect and the driver operated normally. When inward bending with aradius of curvature of 1 mm was performed 4,000 times, the displayportion had no defect and the driver operated normally.

FIG. 27A shows the appearance of the light-emitting device after beingsubjected to bending with a radius of curvature of 5 mm 100,000 times.FIG. 27B shows display states before and after the bending test. Asshown in FIG. 27A, warpage due to bending and a scratch on a surfacewere caused in the light-emitting device; however, the display state andthe operation of the driver had no problem. Furthermore, a preservationtest was performed at a high temperature of 65° C. and a high humidityof 90% for 100 hours after the bending test. FIG. 27C shows displaystates of the light-emitting device before and after the preservationtest. No defect was also observed in the bent portion after thepreservation test, and a crack did not probably occur in the inorganicinsulating film or the like in the light-emitting device.

FIG. 28A shows the appearance of the light-emitting device after beingsubjected to the bending with a radius of curvature of 2 mm 100,000times. FIG. 28B shows display states before and after the bending test.As shown in FIG. 28A, warpage due to bending and a scratch on a surfacewere caused in the light-emitting device; however, the display state andthe operation of the driver had no problem. Furthermore, a preservationtest was performed at a high temperature of 65° C. and a high humidityof 90% for 100 hours after the bending test. FIG. 28C shows displaystates of the light-emitting device before and after the preservationtest. No defect was also observed in the bent portion after thepreservation test, and a crack did not probably occur in the inorganicinsulating film or the like in the light-emitting device.

The result of the bending test with the bend tester involves factorssuch as tensile stress, compressive stress, and friction as well assimple bending.

A bending test performed with a book-type bend tester that is capable ofexamining only resistance to bending is described below. In the bendingtest, the bend tester is repeatedly opened (see FIG. 29A) and closed(see FIG. 29B) like a book. The radius of curvature for bending thelight-emitting device was determined by setting the distance betweenplates when bent.

The bending characteristics of the light-emitting devices examined withthe book-type bend tester are described. When inward bending with eachof radiuses of curvature of 5 mm, 3 mm, and 2 mm was performed 100,000times, the display portion had no defect and the driver operatednormally. When inward bending with a radius of curvature of 1 mm wasperformed 9,000 times, the display portion had no defect and the driveroperated normally. Less warpage due to the bending test was caused inthe case where the book-type bend tester was used than in the case wherethe bend tester described above was used, and almost no warpage wasobserved when bending with a radius of curvature of 5 mm was performedwith the book-type bend tester.

According to this example described above, the flexible light-emittingdevice of one embodiment of the present invention, in which thesubstrate having a coefficient of expansion less than or equal to 27ppm/° C. was used, was found to have high resistance to bending and highreliability. Moreover, according to this example, the flexiblelight-emitting device of one embodiment of the present invention, inwhich the bonding layer having hardness higher than or equal to Shore Dof 80 was used, was found to have high resistance to bending and highreliability.

Example 4

In this example, the flexible light-emitting device of one embodiment ofthe present invention was fabricated and its reliability was evaluated.

Five light-emitting devices were fabricated in this example. A structureand a fabricating method similar to those of the light-emitting devicefabricated in Example 3 are omitted.

A sample 13 and a sample 14 differ from the light-emitting device inExample 3 in that a sheet-like adhesive is used for the bonding layer811 and the bonding layer 841. The thickness of the sheet-like adhesiveused for the sample 13 was 10 μm, and the thickness of the sheet-likeadhesive used for the sample 14 was 20 μm.

The bonding layers were used for attachment while pressure treatment andheating were performed under reduced pressure (approximately 100 Pa) sothat inclusion of air bubbles in the bonding surface can be suppressed.The sheet-like adhesive used for the sample 13 and the sample 14 has lowadhesion at room temperature and exhibits high adhesion when heated at atemperature higher than or equal to 60° C. In this example, thesheet-like adhesive was cured by heating at 80° C. for one hour.

A sample 15 differs from the light-emitting device in Example 3 in thata two-part curable epoxy-based resin having hardness of Shore D of 84 to86, which is similar to the material a used for the sample 1 of Example1, is used for the bonding layer 811 and the bonding layer 841.

A sample 16 differs from the light-emitting device in Example 3 in thata sheet-like adhesive having hardness of Shore D of 58 to 62 is used forthe bonding layer 811 and the bonding layer 841. The sheet-like adhesiveused for the sample 16 was cured in such a manner that both surfaces ofthe adhesive were irradiated with UV light (energy of 3,000 mJ/cm²) witha high-pressure mercury lamp and was heated at 120° C. for one hour.

A sample 17 differs from the light-emitting device in Example 3 in thata two-part curable epoxy-based resin having hardness of Shore D of 84 to86, which is similar to the material a used for the sample 1 of Example1, is used for the bonding layer 811, the bonding layer 823, and thebonding layer 841.

When a preservation test was performed at a high temperature of 65° C.and a high humidity of 90% for 100 hours in the sample 13 and the sample14, the display state and the operation of the driver had no problem.

When, on the sample 13 and the sample 14, inward bending with a radiusof curvature of 3 mm was performed 100,000 times with the bend tester inFIG. 25A, the display portion had no defect and the driver operatednormally.

In the sample 16 in which hardness of the bonding layer 811 and hardnessof the bonding layer 841 are each Shore D of 58 to 62, a crack hasalready occurred in the fabricating process. On the other hand, in thesample 15 in which hardness of the bonding layer 811 and hardness of thebonding layer 841 are each Shore D of 84 to 86, a crack was not observedin the fabricated light-emitting device. When a preservation test wasperformed at a high temperature of 65° C. and a high humidity of 90% for500 hours in the sample 15 and the sample 16, there were less shrinkage(here, luminance decay from the end portion of the light-emittingportion or expansion of a non-light-emitting region of thelight-emitting portion) than in the sample 15 and the sample 16.Accordingly, the reliability of the light-emitting device was found tobe improved by suppressing occurrence of a crack in the inorganicinsulating film or the element in the fabricating process of thelight-emitting device.

When, on the sample 17, inward bending with a radius of curvature of 5mm was performed 100,000 times with the bend tester in FIG. 25A, thedisplay portion had no defect and the driver operated normally.Furthermore, when, on the sample 17, a preservation test was performedat a high temperature of 65° C. and a high humidity of 95% for 240 hoursafter the bending test, shrinkage was not caused in the bent portion andthus even a minute crack did not occur.

According to this example described above, the flexible light-emittingdevice of one embodiment of the present invention, in which the bondinglayer having hardness higher than or equal to Shore D of 80 was used,was found to have high resistance to bending and high reliability.Moreover, according to this example, the flexible light-emitting deviceof one embodiment of the present invention, in which the sheet-likeadhesive was used, was found to have high resistance to bending and highreliability.

Example 5

Examples of time taken to form the base film, the peeling layer 103, andthe insulating layer 813 formed in Example 1 will be described.

Table 3 shows deposition methods of layers for forming the base film,the peeling layer 103, and the insulating layer 813, processing time perbatch, and processing time per substrate.

TABLE 3 takt time thick- takt time per sub- ness deposition per batchstrate (nm) method (min) (min) insulating third silicon 100 batch 52 5.2layer 813 oxynitride film processing silicon nitride 140 oxide filmsecond silicon 200 oxynitride film silicon nitride 200 film firstsilicon 600 batch 20 2 oxynitride film processing peeling tungsten film30 single wafer — 2 layer 103 processing base film silicon 200 batch 444.4 oxynitride film processing

Here, the base film, the peeling layer 103, and the first siliconoxynitride film were each formed in a single layer, and the other fourlayers of the insulating layer 813 were formed collectively. Thetungsten film was formed with a single-wafer sputtering apparatus, andthe other layers were formed with a batch type CVD apparatus.

Note that the takt time in Table 3 does not include time fortransferring substrates. As for the takt time of the batch processing,the takt time per batch and the takt time per substrate (the valueobtained by dividing the takt time per batch by the number of substratesprocessed, and here 10 substrates were processed per batch) are shown.

In this example, fabrication by a device which is suitable for massproduction is not performed; therefore, the takt time is probablyfurther shortened depending on the specification of the device.Moreover, even when a structure that has both peelability and amoisture-proof property is applied to the inorganic films for formingthe peeling layer and the insulating layer, it was found that depositionat an extremely low rate is not needed and a highly reliable device canbe manufactured with high productivity.

Example 6

In this example, yield of each step and time taken for each step in themethod for manufacturing the device of one embodiment of the presentinvention will be described.

The method for manufacturing the device of one embodiment of the presentinvention which is described in Embodiment 2 as an example (see FIGS.15A to 15C, FIGS. 16A to 16C, and FIGS. 17A and 17B) includes a firstprocess of performing first peeling of a formation substrate and firstattachment of a flexible substrate, a second process of performingsecond peeling of the formation substrate and second attachment of theflexible substrate, and a third process of exposing a conductive layerelectrically connected to an FPC and attaching the FPC by pressure.

Note that in this example, the formation substrate 201 over which atransistor or an organic EL element was formed was peeled in the firstprocess, and the formation substrate 221 on which a color filter or thelike was formed was peeled in the second process. The hardness of eachof the bonding layer 823, the bonding layer 811, and the bonding layer841 was set to be higher than or equal to Shore D of 80. As thematerial, a two-part curable epoxy-based resin was used instead of asheet-like adhesive. A flexible substrate having a coefficient ofexpansion less than or equal to 27 ppm/° C. was used as the substrate801 and the substrate 803.

First, a 3.4-inch flexible organic EL display was fabricated with aformation substrate having 5 inches on each side, and yield was checkedin the above three processes.

As shown in Table 4, when 221 displays were manufactured, the yield ineach step was 90% or more and the total yield was 83%.

TABLE 4 first process second process third process total yield 91.40%95.00% 95.80% 83.20% (202/221) (192/202) (184/192) (184/221)

Furthermore, a 5.3-inch flexible organic EL display was fabricated witha formation substrate sized 300 mm×360 mm, and yield was checked in theabove three processes. Note that two displays were taken out from theformation substrate.

As shown in Table 5, when 76 displays were manufactured in total usingthe 38 formation substrates, the yield in each step was 90% or more andthe total yield was 84%.

TABLE 5 first process second process third process total yield 92.10%91.40% 100.00% 84.20% (70/76) (64/70) (64/64) (64/76)

By mixture of a foreign substance in the fabricating process, forexample, film peeling in an organic film at the time of peeling can begiven as one mode of defects. The displays were fabricated manually inthis example; therefore, the yield can be probably improved with amanufacturing apparatus. In addition, it was found that the yield isunlikely to be decreased even when the formation substrate is increasedin size.

Table 6 shows time taken in each step when a 13.5-inch flexible organicEL display is fabricated manually using a formation substrate sized 300mm×360 mm.

TABLE 6 time (min) formation of peeling starting point 5 peeling offormation substrate 201 5 cleaning 7 attachment of substrate 801 10baking at 40° C. for curing of 720 bonding layer 811 baking at 80° C.for curing of 30 bonding layer 811 formation of peeling starting point 5peeling of formation substrate 221 3 attachment of substrate 803 10baking at 40° C. for curing of 720 bonding layer 841 exposure ofconductive layer 857 12

In this example, since a two-part curable epoxy-based resin was used asa material of the bonding layer, it takes time to cure the bondinglayer. However, the time taken for a process per display can beshortened by batch processing. According to one embodiment of thepresent invention, a sheet-like adhesive is preferably used, in whichcase the time taken to fabricate the device can be shortened.

Example 7

In this example, conditions for favorably peeling a thin film will bedescribed.

[Method for Examining Peelability]

First, an examination method for peeling a thin film from a supportsubstrate will be described.

The force required for peeling may be examined with a jig illustratedin, for example, FIG. 30A. The jig illustrated in FIG. 30A includes aplurality of guide rollers 7606 and a plurality of support rollers 7605.A tape 7604 is attached onto a thin film 7603 which is formed over asupport substrate 7601 and an end portion of the tape 7604 is partlypeeled in advance. Then, the support substrate 7601 is fixed to the jigso that the tape 7604 is held by the support rollers 7605, and the tape7604 and the thin film 7603 are positioned perpendicular to the supportsubstrate 7601. The force required for peeling can be measured asfollows: when the tape 7604 is pulled perpendicular to the supportsubstrate 7601 to peel the thin film 7603 from the support substrate7601, the force required for the pulling in the perpendicular directionis measured. During the peeling, the support substrate 7601 moves in theplane direction along the guide rollers 7606 with a peeling layer 7602exposed. The support rollers 7605 and the guide rollers 7606 arerotatable so that the thin film 7603 and the support substrate 7601 arenot affected by friction during the move.

In a sample for a peeling test shown below, the support substrate wascut into a size of 25 mm×126.6 mm, and a UV curable adhesive film (alsoreferred to as a UV film; UHP-0810MC manufactured by DENKI KAGAKU KOGYOKABUSHIKI KAISHA) was attached as the tape 7604 to the cut supportsubstrate by a tape mounter. After that, an approximately 20 mm of anend portion of the UV film was peeled, and the sample was fixed to thejig. For the peeling test, a compact table-top universal tester (EZ-TESTEZ-S-50N) manufactured by Shimadzu Corporation was used. For the peelingtest, an adhesive tape/adhesive sheet testing method based on standardnumber JIS Z0237 of Japanese Industrial Standards (JIS) was referred to.

[Structure of Sample]

The structure of the sample used for examination is described. FIG. 30Billustrates the cross-sectional structure of the sample. In the sample,a peeling layer 7612, a first layer 7613, and a second layer 7614 arestacked in this order over a support substrate 7611. Peeling occurs atan interface between the peeling layer 7612 and the first layer 7613.

[Relation Between Peelability and Hydrogen Releasing Property]

Here, the relation between peelability and the amount of releasedhydrogen in the first layer is described.

<Samples A to C>

In a sample A, a sample B, and a sample C, a glass substrate over whichan approximately 200-nm-thick silicon oxynitride film was formed wasused as the support substrate 7611. An approximately 30-nm-thicktungsten film was formed as the peeling layer 7612 by a sputteringmethod. A silicon oxynitride film was formed as the first layer 7613 bya plasma CVD method. Subsequently, an approximately 200-nm-thick siliconnitride film, an approximately 200-nm-thick silicon oxynitride film, anapproximately 140-nm-thick silicon nitride oxide film, and anapproximately 100-nm-thick silicon oxynitride film were formed in thisorder as the second layer 7614 by a plasma CVD method. After that, heattreatment was performed at 450° C. for one hour.

In the sample A, the thickness of the first layer 7613 was set to beapproximately 600 nm. In the sample B, the thickness of the first layer7613 was set to be approximately 400 nm. In the sample C, the thicknessof the first layer 7613 was set to be approximately 200 nm.

Here, as for the approximately 600-nm-thick silicon oxynitride film usedfor the sample A and the approximately 200-nm-thick silicon oxynitridefilm used for the sample C, FIG. 31A shows results of examiningtemperature dependence of intensity detected at the mass-to-charge ratio(m/z) of 2 corresponding to a hydrogen molecule by thermal desorptionspectroscopy (TDS) analysis. The results showed that the larger thethickness of the silicon oxynitride film was, the larger the amount ofreleased hydrogen tended to be.

Subsequently, force required for peeling in the samples A to C wasmeasured. For each sample, six samples which were cut from the samesubstrate according to the above-described size were measured. FIG. 31Bshows measurement results. As a result, the force required for peelingin the sample A was the smallest, and the force required for peeling inthe sample C was the largest.

<Samples D to F>

In a sample D, a sample E, and a sample F, a glass substrate over whichan approximately 200-nm-thick silicon oxynitride film was formed wasused as the support substrate 7611. An approximately 30-nm-thicktungsten film was formed as the peeling layer 7612 by a sputteringmethod. An approximately 600-nm-thick silicon oxynitride film was formedas the first layer 7613 by a plasma CVD method. Subsequently, anapproximately 200-nm-thick silicon nitride film was formed as the secondlayer 7614 by a plasma CVD method. After that, heat treatment wasperformed at 450° C. for one hour.

Here, as the film formation conditions of the silicon oxynitride filmused for the first layer 7613, the flow rates of silane in the sample D,the sample E, and the sample F were set to be 50 sccm, 75 sccm, and 100sccm, respectively.

FIG. 32A shows the results of TDS analysis of the samples D to F. Theresults showed that the larger the amount of silane at the filmformation of the silicon oxynitride film was, the larger the amount ofreleased hydrogen tended to be.

Subsequently, FIG. 32B shows measurement results of force required forpeeling in the samples D to F. In the sample D, none of the measured sixsamples was able to be peeled favorably. In the sample E and the sampleF, all of the measured six samples were able to be peeled favorably.Moreover, the force required for peeling of the sample F was smallerthan that of the sample E.

<Samples M to O>

In a sample M, a sample N, and a sample O, a glass substrate over whichan approximately 200-nm-thick silicon oxynitride film was formed wasused as the support substrate 7611. An approximately 30-nm-thicktungsten film was formed as the peeling layer 7612 by a sputteringmethod. An approximately 600-nm-thick silicon oxynitride film was formedas the first layer 7613 by a plasma CVD method. Subsequently, anapproximately 200-nm-thick silicon nitride film was formed as the secondlayer 7614 by a plasma CVD method. After that, heat treatment wasperformed at 450° C. for one hour.

Here, the approximately 200-nm-thick silicon oxynitride film, thesilicon oxynitride film used for the first layer 7613, and the siliconnitride film used for the second layer 7614 were formed using anapparatus different from the apparatus used for the samples D to F.Specifically, a film formation apparatus which was smaller than the filmformation apparatus used for the samples D to F in an electrode area,chamber capacity, and the like was used.

In addition, as the film formation conditions of the silicon oxynitridefilm used for the first layer 7613, the flow rates of silane in thesample M, the sample N, and the sample O were set to be 5 sccm, 27 sccm,and 60 sccm, respectively.

FIG. 35A shows the results of TDS analysis of the samples M to O. Theresults showed that the larger the amount of silane at the filmformation of the silicon oxynitride film was, the larger the amount ofreleased hydrogen tended to be.

Subsequently, FIG. 35B shows measurement results of force required forpeeling in the samples M to O. In the sample M, neither of the measuredtwo samples was able to be peeled favorably. In the sample N and thesample O, both of the measured two samples were able to be peeledfavorably. Moreover, the force required for peeling of the sample O wassmaller than that of the sample N.

<Samples P to R>

In a sample P, a sample Q, and a sample R, a glass substrate over whichan approximately 200-nm-thick silicon oxynitride film was formed wasused as the support substrate 7611. An approximately 30-nm-thicktungsten film was formed as the peeling layer 7612 by a sputteringmethod. An approximately 600-nm-thick silicon oxynitride film was formedas the first layer 7613 by a plasma CVD method. Subsequently, anapproximately 200-nm-thick silicon nitride film was formed as the secondlayer 7614 by a plasma CVD method. After that, heat treatment wasperformed at 450° C. for one hour.

Here, as the film formation conditions of the silicon oxynitride filmused for the first layer 7613, the power densities in the sample P, thesample Q, and the sample R were set to be 0.041 W/cm², 0.071 W/cm², and0.204 W/cm², respectively.

FIG. 36A shows the results of TDS analysis of the samples P to R. Theresults showed that the lower the power density at the film formation ofthe silicon oxynitride film was, the larger the amount of releasedhydrogen tended to be.

Subsequently, FIG. 36B shows measurement results of force required forpeeling in the samples P to R. In the sample R, neither of the measuredtwo samples was able to be peeled favorably. In the sample P and thesample Q, both of the measured two samples were able to be peeledfavorably. Moreover, the force required for peeling of the sample P wassmaller than that of the sample Q.

The above results showed that the larger the amount of hydrogen releasedfrom the first layer 7613 was, the smaller the force required forpeeling was.

Moreover, the amount of released hydrogen was able to be controlled bythe film formation conditions of the silicon oxynitride film used forthe first layer 7613. Specifically, a silicon oxynitride film which wassuitable for peeling and had a large amount of released hydrogen wasable to be fabricated depending on the conditions of a film thickness, aflow rate of silane with respect to a deposition gas, power density, orthe like.

[Relation Between Peelability and Heat Treatment Temperature]

Here, the relation between peelability and the temperature of heattreatment performed after the formation of the second layer 7614 isdescribed.

<Samples G to J>

A sample G, a sample H, a sample I, and a sample J were each fabricatedin a manner similar to that of the sample A except the condition of heattreatment.

A sample obtained by heat treatment at 350° C. for one hour performedafter the formation of the second layer 7614 was the sample G.Similarly, a sample obtained by heat treatment at 400° C. for one hour,a sample obtained by heat treatment at 450° C. for one hour, and asample obtained by heat treatment at 480° C. for one hour were thesample H, the sample I, and the sample J, respectively.

FIG. 33 shows measurement results of force required for peeling in thesamples G to J. In the sample G, none of the measured three samples wasable to be peeled favorably. In the samples H to J, all of the measuredthree samples were able to be peeled favorably. The sample I and thesample J were equivalent in the force required for peeling. The forcerequired for peeling in the sample H was stronger than those in thesample I and the sample J.

The above results showed that the higher the temperature of the heattreatment after the formation of the second layer 7614 was, the morepeelability was improved, and that peelability was saturated at atemperature higher than or equal to a predetermined temperature. It isprobable that the amount of hydrogen released from the first layer 7613was increased and peelability was improved as the temperature of theheat treatment got higher.

[Relation Between Peelability and Hydrogen-Blocking Property of SecondLayer]

Here, the relation between peelability and the hydrogen-blockingproperty of the second layer 7614 is described.

<Samples K and L>

In a sample K and a sample L, a glass substrate over which anapproximately 200-nm-thick silicon oxynitride film was formed was usedas the support substrate 7611. An approximately 30-nm-thick tungstenfilm was formed as the peeling layer 7612 by a sputtering method.Subsequently, an approximately 600-nm-thick silicon oxynitride film wasformed as the first layer 7613 by a plasma CVD method.

Only in the sample K, an approximately 200-nm-thick silicon nitride filmwas formed as the second layer 7614 by a plasma CVD method. After that,heat treatment was performed at 450° C. for one hour. In the sample L,the second layer 7614 was not formed.

First, FIG. 34A shows the results of TDS analysis of the approximately600-nm-thick silicon oxynitride film used for the first layer 7613, theapproximately 200-nm-thick silicon nitride film used for the secondlayer 7614, and a stack of the silicon oxynitride film and the siliconnitride film. Although the silicon oxynitride film was found to releasea large amount of hydrogen, the silicon nitride was found to releasehydrogen hardly compared with the silicon oxynitride film. Moreover, theamount of hydrogen that diffuses above was reduced by stacking thesilicon nitride film over the silicon oxynitride film. This result showsthat the silicon nitride film has a blocking property against hydrogen.

Subsequently, FIG. 34B shows measurement results of force required forpeeling in the samples K and L. In the sample K, both of the measuredtwo samples were able to peel be peeled favorably. On the other hand, inthe sample L in which the second layer 7614 was not formed, neither ofthe measured two samples was able to be peeled favorably.

According to the above result, providing the second layer 7614 having ablocking property against hydrogen was found to suppress upwarddiffusion of hydrogen released from the first layer 7613 and increasethe amount of hydrogen that contributes to peeling, resulting in anincrease of peelability.

REFERENCE NUMERALS

98: rod, 99: light-emitting device, 101: formation substrate, 103:peeling layer, 104: insulating layer, 105: layer to be peeled, 106:element layer, 107: bonding layer, 109: substrate, 111: bonding layer,112: bonding layer, 113: resin layer, 114: substrate, 115: laser lightirradiation region, 117: peeling starting portion, 171: bonding layer,173: substrate, 201: formation substrate, 203: peeling layer, 204:insulating layer, 205: layer to be peeled, 206: element layer, 207:bonding layer, 221: formation substrate, 223: peeling layer, 224:insulating layer, 225: layer to be peeled, 226: functional layer, 231:substrate, 233: bonding layer, 301: display portion, 302: pixel, 302B:sub-pixel, 302G: sub-pixel, 302R: sub-pixel, 302 t: transistor, 303 c:capacitor, 303 g(1): scan line driver circuit, 303 g(2): imaging pixeldriver circuit, 303 s(1): imaging signal line driver circuit, 303 s(2):imaging signal driver circuit, 303 t: transistor, 304: gate, 308:imaging pixel, 308 p: photoelectric conversion element, 308 t:transistor, 309: FPC, 310: portable information terminal, 311: wiring,312: display panel, 313: hinge, 315: housing, 319: terminal, 320:portable information terminal, 321: insulating layer, 322: displayportion, 325: non-display portion, 328: partition, 329: spacer, 330:portable information terminal, 333: display portion, 335: housing, 336:housing, 337: information, 339: operation button, 340: portableinformation terminal, 345: portable information terminal, 350R:light-emitting element, 351: housing, 351R: lower electrode, 352: upperelectrode, 353: EL layer, 353 a: EL layer, 353 b: EL layer, 354:intermediate layer, 355: data, 356: data, 357: data, 358: displayportion, 360: bonding layer, 367BM: light-blocking layer, 367 p:anti-reflective layer, 367R: coloring layer, 380B: light-emittingmodule, 380G: light-emitting module, 380R: light-emitting module, 390:touch panel, 501: display portion, 502R: sub-pixel, 502 t: transistor,503 c: capacitor, 503 g: scan line driver circuit, 503 t: transistor,505: touch panel, 505B: touch panel, 509: FPC, 510: substrate, 510 a:insulating layer, 510 b: flexible substrate, 510 c: bonding layer, 511:wiring, 519: terminal, 521: insulating film, 528: partition, 550R:light-emitting element, 560: bonding layer, 567BM: light-blocking layer,567 p: anti-reflective layer, 567R: coloring layer, 570: substrate, 570a: insulating layer, 570 b: flexible substrate, 570 c: bonding layer,580R: light-emitting module, 590: substrate, 591: electrode, 592:electrode, 593: insulating layer, 594: wiring, 595: touch sensor, 597:bonding layer, 598: wiring, 599: bonding layer, 801: substrate, 803:substrate, 804: light-emitting portion, 806: driver circuit portion,808: FPC, 811: bonding layer, 813: insulating layer, 814: conductivelayer, 815: insulating layer, 816: conductive layer, 817: insulatinglayer, 817 a: insulating layer, 817 b: insulating layer, 820:transistor, 821: insulating layer, 822: transistor, 823: bonding layer,824: bonding layer, 825: connector, 827: spacer, 830: light-emittingelement, 831: lower electrode, 833: EL layer, 835: upper electrode, 841:bonding layer, 843: insulating layer, 845: coloring layer, 847:light-blocking layer, 849: overcoat, 857: conductive layer, 857 a:conductive layer, 857 b: conductive layer, 862: EL layer, 864:conductive layer, 7100: portable information terminal, 7101: housing,7102: display portion, 7103: band, 7104: buckle, 7105: operation button,7106: input/output terminal, 7107: icon, 7200: lighting device, 7201:stage, 7202: light-emitting portion, 7203: operation switch, 7210:lighting device, 7212: light-emitting portion, 7220: lighting device,7222: light-emitting portion, 7300: display device, 7301: housing, 7302:display portion, 7303: operation button, 7304: display portion pull,7305: control portion, 7400: cellular phone, 7401: housing, 7402:display portion, 7403: operation button, 7404: external connection port,7405: speaker, 7406: microphone, 7601: support substrate, 7602: peelinglayer, 7603: thin film, 7604: tape, 7605: support roller, 7606: guideroller, 7611: support substrate, 7612: peeling layer, 7613: layer, and7614: layer.

This application is based on Japanese Patent Application serial no.2014-029756 filed with Japan Patent Office on Feb. 19, 2014, the entirecontents of which are hereby incorporated by reference.

1. A light-emitting device comprising: a first substrate havingflexibility; a second substrate having flexibility; an element layerbetween the first substrate and the second substrate; an insulatinglayer between the first substrate and the element layer; a first bondinglayer between the first substrate and the insulating layer; and a secondbonding layer between the second substrate and the element layer,wherein an end portion of the first bonding layer be positioned on aninner side than an end portion of the insulating layer, wherein theelement layer comprises a light-emitting element, wherein the firstsubstrate comprises a third portion whose coefficient of expansion isless than 58 ppm/° C., and wherein the second substrate comprises afourth portion whose coefficient of expansion is less than 58 ppm/° C.2. The light-emitting device according to claim 1, wherein the firstbonding layer comprises a first portion whose hardness is higher thanShore D of 70, and wherein the second bonding layer comprises a secondportion whose hardness is higher than Shore D of
 70. 3. Thelight-emitting device according to claim 1, wherein the coefficient ofexpansion of the third portion is less than or equal to 30 ppm/° C., andwherein the coefficient of expansion of the fourth portion is less thanor equal to 30 ppm/° C.
 4. The light-emitting device according to claim1, wherein the insulating layer comprises: a first silicon oxynitridefilm; a silicon nitride film over the first silicon oxynitride film; asecond silicon oxynitride film over the silicon nitride film; a siliconnitride oxide film over the second silicon oxynitride film; and a thirdsilicon oxynitride film over the silicon nitride oxide film.
 5. Thelight-emitting device according to claim 1, wherein the first bondinglayer comprises an epoxy resin, and wherein the second bonding layercomprises an epoxy resin.
 6. A light-emitting device comprising: a firstsubstrate having flexibility; a second substrate having flexibility; anelement layer between the first substrate and the second substrate; aninsulating layer between the first substrate and the element layer; afirst bonding layer between the first substrate and the insulatinglayer; and a second bonding layer between the second substrate and theelement layer, wherein an end portion of the first bonding layer bepositioned on an inner side than an end portion of the insulating layer,wherein the element layer comprises a light-emitting element, whereinthe first substrate comprises a third portion whose coefficient ofexpansion is less than 58 ppm/° C., wherein the second substratecomprises a fourth portion whose coefficient of expansion is less than58 ppm/° C., and wherein a display portion comprising the light-emittingelement is a curved display portion.
 7. The light-emitting deviceaccording to claim 6, wherein a display surface of the display portionis bent.
 8. The light-emitting device according to claim 6, wherein ahousing of the light-emitting device comprises a front surface and aside surface, and wherein the display portion comprises a regioncorresponding to the front surface and a region corresponding to theside surface.
 9. The light-emitting device according to claim 6, whereina housing of the light-emitting device comprises a front surface, ashorter side surface, and a longer side surface, and wherein the displayportion comprises a region corresponding to the front surface, a regioncorresponding to the shorter side surface, and a region corresponding tothe longer side surface.
 10. A portable information terminal comprisingthe light-emitting device according to claim
 6. 11. The light-emittingdevice according to claim 6, wherein the first bonding layer comprisesan epoxy resin, and wherein the second bonding layer comprises an epoxyresin.
 12. A light-emitting device comprising: a first substrate havingflexibility; a second substrate having flexibility; an element layerbetween the first substrate and the second substrate; an insulatinglayer between the first substrate and the element layer; a first bondinglayer between the first substrate and the insulating layer; and a secondbonding layer between the second substrate and the element layer,wherein an end portion of the first bonding layer be positioned on aninner side than an end portion of the insulating layer, wherein theelement layer comprises a light-emitting element, wherein the firstsubstrate comprises a third portion whose coefficient of expansion isless than 58 ppm/° C., wherein the second substrate comprises a fourthportion whose coefficient of expansion is less than 58 ppm/° C., andwherein the light-emitting device is a foldable light-emitting device.13. The light-emitting device according to claim 12, wherein thelight-emitting device is foldable so that a first region of a displaysurface of the light-emitting device and a second region of the displaysurface face each other.
 14. The light-emitting device according toclaim 12, wherein the light-emitting device is foldable so that a firstregion of a display surface of the light-emitting device and a secondregion of the display surface do not face each other.
 15. Thelight-emitting device according to claim 12, wherein the light-emittingdevice is foldable so that a first region of a display surface of thelight-emitting device and a second region of the display surface faceeach other and the second region of the display surface and a thirdregion of the display surface do not face each other.
 16. A portableinformation terminal comprising the light-emitting device according toclaim
 12. 17. The light-emitting device according to claim 12, whereinthe first bonding layer comprises an epoxy resin, and wherein the secondbonding layer comprises an epoxy resin.